Pattern wafer for LEDs, epitaxial wafer for LEDs and method of manufacturing the epitaxial wafer for LEDs

ABSTRACT

A pattern wafer ( 10 ) for LEDs is provided with an uneven structure A ( 20 ) having an arrangement with n-fold symmetry substantially on at least a part of the main surface, where in at least a part of the uneven structure A ( 20 ), a rotation shift angle Θ meets 0°&lt;Θ≦(180/n)° in which Θ is the rotation shift angle of an arrangement axis A of the uneven structure A ( 20 ) with respect to a crystal axis direction in the main surface, and a top of the convex-portion of the uneven structure A ( 20 ) is a corner portion with a radius of curvature exceeding “0”. A first semiconductor layer ( 30 ), light emitting semiconductor layer ( 40 ) and second semiconductor layer ( 50 ) are layered on the uneven structure A ( 20 ) to constitute an epitaxial wafer ( 100 ) for LEDs. It is possible to provide the pattern wafer for LEDs and epitaxial wafer for LEDs with cracks and internal quantum efficiency IQE improved.

TECHNICAL FIELD

The present invention relates to a pattern wafer for LEDs, epitaxialwafer for LEDs and method of manufacturing the epitaxial wafer for LEDs

BACKGROUND ART

A semiconductor light emitting device chip e.g. LED chip is generallymanufactured by manufacturing an epitaxial wafer for LEDs obtained bysequentially layering and growing a first semiconductor layer, lightemitting semiconductor layer and second semiconductor layer that are oflight emitting diode structure on a wafer for LEDs, subsequently formingelectrodes respectively on the second semiconductor layer and firstsemiconductor layer, and making a chip. Then, emitted light generateddue to recombination of a hole and an electron injected from respectivesemiconductor layers is extracted to the outside of the LED chip, andthe light emission of the LED is visually identified. In addition,generally adopted is the structure where the emitted light is extractedfrom the transparent electrode side on the second semiconductor layer orthe wafer for LEDs side, and it is also possible to remove the wafer forLEDs to extract the emitted light from the first semiconductor layerside.

As factors to determine external quantum efficiency EQE indicative ofefficiency of an LED, there is electron injection efficiency EIE,internal quantum efficiency IQE, and light extraction efficiency LEE.Among the factors, the internal quantum efficiency IQE is dependent onthe dislocation density caused by lattice mismatch of the semiconductorcrystal (for example, Non-patent Document 1). The light extractionefficiency LEE is improved by disturbing the waveguide mode inside thesemiconductor layer by light scattering due to an uneven structureprovided on the pattern wafer for LEDs (for example, Patent Document 1).Further, the electron injection efficiency EIE is improved by reducinginterface resistance between the second semiconductor layer and thetransparent conductive comprised of oxide such as ITO, ZnO, In₂O₃, andSnO₂.

The external quantum efficiency EQE of an LED is determined by threefactors as described above, and the internal quantum efficiency IQEmeans efficiency itself that the LED emits light, and is not expected toundergo significant improvements when the first semiconductor layer,light emitting semiconductor layer and second semiconductor layer aredeposited on a pattern wafer for LEDs to manufacture the epitaxial waferfor LEDs. In other words, in order to manufacture LEDs for actualizinghigh external quantum efficiency EQE, it is necessary to improve atleast the internal quantum efficiency IQE.

From such a background, in order to significantly improve the internalquantum efficiency IQE, proposed is an LED manufactured by depositing asemiconductor layer on an uneven structure of a pattern wafer for LEDsbeforehand provided with the uneven structure on the surface of thewafer for LEDs (for example, see Non-patent Document 2).

PRIOR ART DOCUMENT Patent Document

-   [Patent Document 1] Japanese Unexamined Patent Publication No.    2009-200514

Non-Patent Document

-   [Non-patent Document 1] IEEE photo. Tech. Lett., 20, 13 (2008)-   [Non-patent Document 2] J. Appl. Phys., 103, 014314 (2008)

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

However, in the case where the uneven structure is provided on a waferfor LEDs so as to improve the internal quantum efficiency IQE, thesemiconductor layer-growth are not stabilized, uneven structure is notflattened sufficiently by the semiconductor layer, and there is aproblem that cracks occur in the semiconductor layer. By generation ofsuch cracks, light emitting diode characteristics of the epitaxial waferfor LEDs degrade significantly, and the defect rate of LED chipsincreases.

The present invention was made in view of the above-mentioned problem,and it is an object of the invention to provide a pattern wafer for LEDsfor enabling a semiconductor layer with the internal quantum efficiencyIQE improved to be deposited while suppressing the occurrence of cracks,an epitaxial wafer for LEDs with cracks and internal quantum efficiencyIQE improved, and a method of manufacturing the epitaxial wafer forLEDs.

Means for Solving the Problem

A pattern wafer for LEDs of the present invention is characterized bybeing provided with an uneven structure A having an arrangement withn-fold symmetry substantially on at least a part of a main surface,where in at least a part of the uneven structure A, a rotation shiftangle Θ meets 0°<Θ≦(180/n)° in which Θ is the rotation shift angle of anarrangement axis A of the uneven structure A with respect to a crystalaxis direction of the pattern wafer for LEDs in the main surface, and atop of the convex-portion of the uneven structure A is a corner portionwith a radius of curvature exceeding “0”.

Further, an epitaxial wafer for LEDs of the invention is characterizedin that at least a first semiconductor layer, a light emittingsemiconductor layer and a second semiconductor layer are layered in thisorder on the main surface provided with the uneven structure A of thepattern wafer for LEDs.

A method of manufacturing an epitaxial wafer for LEDs of the inventionis characterized by including the steps of preparing a pattern wafer forLEDs, the step of performing an optical inspection on the preparedpattern wafer for LEDs, and the step of manufacturing an epitaxial waferfor LEDs using the pattern wafer for LEDs subjected to the opticalinspection.

Advantageous Effect of the Invention

According to the present invention, the internal quantum efficiency IQEis improved by dispersing dislocations generated in the semiconductorlayer by the uneven structure A of the pattern wafer for LEDs anddecreasing the dislocation density. At the same time, by setting therotation shift angle Θ between the crystal axis of the pattern wafer forLEDs and the arrangement axis A of the uneven structure A in apredetermined range, it is possible to suppress cracks occurring in thesemiconductor layer. In other words, it is possible to manufacture theepitaxial wafer for LEDs with excellent light emitting diodecharacteristics, and in association therewith, it is possible toefficiently manufacture LED chips with high external quantum efficiencyEQE.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 contains schematic diagrams to explain a rotation shift angle Θmade by a crystal axis of a pattern wafer (1) for LEDs and anarrangement axis A of an uneven structure A according to thisEmbodiment;

FIG. 2 is a schematic diagram showing an arrangement example of theuneven structure A having 3-fold symmetry or more in the pattern wafer(1) for LEDs according to this Embodiment;

FIG. 3 is a schematic diagram showing another arrangement example of theuneven structure A having 3-fold symmetry or more in the pattern wafer(1) for LEDs according to this Embodiment;

FIG. 4 is a schematic diagram to explain the crystal axis of a crystallattice in the main surface of the pattern wafer (1) for LEDs accordingto this Embodiment;

FIG. 5 contains schematic diagrams illustrating surface observationimages when deposition is stopped in a nucleus growth stage indepositing a semiconductor layer on the surface of the pattern wafer (1)for LEDs;

FIG. 6 is a graph illustrating the relationship among the rotation shiftangle Θ, a size of a bottom of the concave-portion contributing togrowth of the semiconductor layer and a density of convex portions thatthe growing semiconductor layer passes in the case of growing thesemiconductor layer on the pattern wafer (1) for LEDs;

FIG. 7 is a graph illustrating the relationship among Duty, the size ofthe bottom of the concave-portion contributing to growth of thesemiconductor layer and the density of convex portions that the growingsemiconductor layer passes in the case of growing the semiconductorlayer on the pattern wafer (1) for LEDs;

FIG. 8 is a graph illustrating the relationship between the rotationshift angle Θ and the Duty shown in FIGS. 6 and 7;

FIG. 9 is a graph illustrating the relationship between average intervalPave and Duty of the uneven structure A of the pattern wafer (1) forLEDs according to this Embodiment;

FIG. 10A is a scanning electron microscope photograph showing an exampleof a cross-sectional shape of the top of the convex-portion of theuneven structure. A according to this Embodiment, FIG. 10B is aschematic diagram indicating a part of FIG. 10A;

FIG. 11 is a scanning electron microscope photograph showing an exampleof an undoped first semiconductor layer according to this Embodiment;

FIG. 12A contains scanning electron microscope photographs showingcracks, FIG. 12B contains schematic diagrams indicating a part of FIG.12A;

FIG. 13 is a graph illustrating the relationship between the crackdensity and Full Width Half Maximum (FWHM) of a rocking curve;

FIG. 14 is a graph illustrating the relationship between the crackdensity and a dark spot density obtained from an image obtained bycathode luminescence (CL) evaluation;

FIG. 15 contains scanning electron microscope photographs showingexamples of the cross-sectional shape of the top of the convex-portionof the uneven structure A according to this Embodiment;

FIG. 16 is a diagram of a graph illustrating the relationship betweenaverage interval Pave and Duty of the uneven structure A of the patternwafer (1) for LEDs according to this Embodiment;

FIG. 17 is another graph illustrating the relationship between averageinterval Pave and Duty of the uneven structure A of the pattern wafer(1) for LEDs according to this Embodiment;

FIG. 18 contains explanatory diagrams illustrating the relationshipbetween an uneven structure G and a non-G region in the pattern wafer(1) for LEDs according to this Embodiment;

FIG. 19 contains schematic diagrams illustrating contour shapes formedby the uneven structure G region in the pattern wafer (1) for LEDsaccording to this Embodiment;

FIG. 20 contains plan schematic diagrams illustrating states obtained byobserving, from a surface, the pattern wafer (1) for LEDs according tothis Embodiment;

FIG. 21 contains plan schematic diagrams illustrating states obtained byobserving, from a surface, the pattern wafer (1) for LEDs according tothis Embodiment;

FIG. 22 is a cross-sectional schematic diagram showing an example of anepitaxial wafer for LEDs according to this Embodiment;

FIG. 23 is a cross-sectional schematic diagram showing another exampleof the epitaxial wafer for LEDs according to this Embodiment;

FIG. 24 is a cross-sectional schematic diagram showing still anotherexample of the epitaxial wafer for LEDs according to this Embodiment;

FIG. 25 is a cross-sectional schematic diagram illustrating an LED chipaccording to this Embodiment;

FIG. 26 is a cross-sectional schematic diagram showing another exampleof the LED chip according to this Embodiment;

FIG. 27 contains cross-sectional schematic diagrams showing an exampleof a pattern wafer (2) for LEDs according to this Embodiment;

FIG. 28 contains cross-sectional-schematic diagrams showing anotherexample of the pattern wafer (2) for LEDs according to this Embodiment;

FIG. 29 contains schematic diagrams illustrating an uneven structure inthe pattern wafer (2) for LEDs according to this Embodiment; and

FIG. 30 contains cross-sectional schematic diagrams showing anotherexample of the pattern wafer (2) for LEDs according to this Embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

One Embodiment (hereinafter, abbreviated as Embodiment) of the presentinvention will specifically be described below. In addition, the presentinvention is not limited to the following Embodiment, and is capable ofbeing carried into practice with various modifications thereof withinthe scope of the subject matter thereof.

A pattern wafer (1) for LEDs according to this Embodiment ischaracterized by being provided with an uneven structure A having anarrangement with n-fold symmetry substantially on a main surface, wherein at least a part of the uneven structure A, a rotation shift angle Θmeets 0°<Θ≦(180/n)° in which Θ is the rotation shift angle of anarrangement axis A of the uneven structure A with respect to a crystalaxis direction of the pattern wafer (1) for LEDs in the main surface,and a top of the convex-portion of the uneven structure A is a cornerportion with a radius of curvature exceeding “0”.

According to this configuration, it is possible to suppress cracksoccurring in a semiconductor layer deposited on the main surfaceprovided with the uneven structure A of the pattern wafer (1) for LEDs.At the same time, it is possible to disperse dislocations generated inthe semiconductor layer and decrease the dislocation density thereof.Accordingly, it is possible to increase the internal quantum efficiencyIQE of an epitaxial wafer for LEDs using the pattern wafer (1) for LEDs,and to increase yield in manufacturing the pattern wafer (1) for LEDs.Further, since it is possible to suppress cracks in the semiconductorlayer of the epitaxial wafer for LEDs, it is possible to decrease thedefect rate of LED chips.

First, a top of the convex-portion of the uneven structure A of thepattern wafer (1) for LEDs is a corner portion with a radius ofcurvature exceeding “0”. Therefore, in depositing the semiconductorlayer on the uneven structure A of the pattern wafer (1) for LEDs, it ispossible to grow the semiconductor layer with a bottom of theconcavo-portion of the uneven structure as the starting-point. In otherwords, the semiconductor layer grows preferentially from the bottom ofthe concavo-portion. Next, the uneven structure A provided on thepattern wafer (1) for LEDs substantially has an arrangement with n-foldsymmetry. Therefore, in the case of noting the initial growth stage ofthe semiconductor layer deposited on the pattern wafer (1) for LEDs, itis possible to uniformly disperse nucleation of the semiconductor layer,and to achieve balance with ununiformity of nucleus growth. Herein, theununiformity is that the semiconductor layer partially rises by nucleusgrowth. In other words, it is possible to disperse the partially raisedsemiconductor layer in the nucleus growth stage. Then, in using thecrystal axis direction on the main surface of the pattern wafer (1) forLEDs as a reference, the arrangement axis A of the uneven structure A isshifted in a predetermined range by a rotation shift angle Θ. By thismeans, it is possible to increase the size of the bottom of theconcavo-portion significantly contributing to initial growth of thesemiconductor layer. At the same time, it is possible to decrease thenumber of convex portions of the uneven structure that the growingsemiconductor layer passes, in the case of viewing from the growthdirection of the semiconductor layer. From the foregoing, coalescence(adherence) properties of growing nucleuses are made excellent when thesemiconductor layer grows. At the same time, in the coalescence, atravelling direction of dislocations inside the semiconductor layer ischanged to an in-plane direction of the pattern wafer (1) for LEDs. Bythis means, collisions between dislocations are effectively induced, andthe internal quantum efficiency IQE is thereby improved. In other words,since it is possible to obtain the semiconductor layer with the internalquantum efficiency IQE improved in a state in which cracks aresuppressed, it is possible to manufacture the epitaxial wafer for LEDshaving excellent light emitting diode characteristics, and inassociation therewith, it is possible to effectively manufacture LEDchips with high external quantum efficiency EQE.

In the pattern wafer (1) for LEDs according to this Embodiment, it ispreferable that an average interval Pave of the uneven structure A meets50 nm≦Pave≦1500 nm.

In this case, increased are both the effect of improving the internalquantum efficiency IQE and the crack suppression effect. First, by theaverage interval Pave meeting the above-mentioned range, since thedensity of concave portions of the uneven structure A increases, it ispossible to increase the frequency of coalescence of growingsemiconductor layers as described already. In other words, it ispossible to increase the frequency that the dislocation inside thesemiconductor layer changes the travelling direction thereof, the effectof reducing dislocations is increased, and the internal quantumefficiency IQE is thereby increased effectively. Further, it is possibleto control the size of the bottom of the concavo-portion significantlycontributing to the initial growth of the semiconductor layer to withina predetermined range. By this means, it is possible to excellently keepnucleus growth of the semiconductor layer in the bottom of theconcave-portion of the uneven structure A. Accordingly, the cracksuppression effect in the semiconductor layer is increased due to thefact that the arrangement axis A of the uneven structure A shifts in apredetermined range by the rotation shift angle Θ.

In the pattern wafer (1) for LEDs according to this Embodiment, in usingDuty that is a ratio (Φave/Pave) of an average diameter (Φave) of thebottom of the convex-portion of the uneven structure A to the averageinterval Pave, it is preferable that the rotation shift angle Θ meets arange of a tan(Duty/2)°≦Θ≦(180/n)°.

In this case, increased are both the effect of internal quantumefficiency IQE improvement and the crack suppression effect in thesemiconductor layer. By the rotation shift angle Θ meeting theabove-mentioned range, it is possible to increase the size of the bottomof the concave-portion of the uneven structure A significantlycontributing to the initial growth of the semiconductor layer, in thedirection approximately perpendicular to the growth direction of thesemiconductor layer in the main surface, and therefore, increased is thesize of the surface with a fast growth rate of the semiconductor layer.By this means, in the case of noting coalescence of growingsemiconductor layers, the interface area of coalescing semiconductorlayers is increased. Further, since it is possible to decrease thenumber of convex portions of the uneven structure A that the surfacewith the fast growth rate crosses, coalescence properties of growingsemiconductor layers are made excellent. From the foregoing, theinternal quantum efficiency IQE is more increased, and cracks occurringin the semiconductor layer are effectively suppressed.

In the pattern wafer for LEDs according to this Embodiment, the patternwafer (1) for LEDs is preferably a sapphire wafer, silicon wafer,silicon carbide wafer or gallium nitride-based wafer.

According to this configuration, since it is made possible to moreeffectively develop the above-mentioned increases of the internalquantum efficiency IQE, suppression of cracks in the semiconductor layerand reduction in production time, it is possible to obtain LED chipswith high internal quantum efficiency IQE with high yield and shortproduction time.

An epitaxial wafer for LEDs according to this Embodiment ischaracterized in that at least a first semiconductor layer, a lightemitting semiconductor layer and a second semiconductor layer arelayered in this order on the main surface provided with the unevenstructure A of the above-mentioned pattern wafer (1) for LEDs.

According to this configuration, from the principles as describedalready, it is possible to manufacture the epitaxial wafer for LEDshaving the semiconductor layers that are of light emitting diodestructure with high internal quantum efficiency IQE and crackssuppressed.

In the epitaxial wafer for LEDs according to this Embodiment, it ispreferable that a ratio (Hbun/Have) of a distance (Hbun) between asurface on the light emitting semiconductor layer side of the patternwafer (1) for LEDs and a surface on the first semiconductor layer sideof the light emitting semiconductor layer to an average height (Have) ofthe uneven structure A meets 2≦Hbun/Have≦300.

According to this configuration, it is possible to efficientlymanufacture the epitaxial wafer for LEDs with high internal quantumefficiency IQE and cracks suppressed. By the uneven structure A providedon the main surface of the pattern wafer (1) for LEDs, from theprinciples as described already, it is possible to increasecrystallinity of the first semiconductor layer and suppress cracks.Particularly, since the ratio (Hbun/Have) is 2 or more, the degree offlattening of the uneven structure A is increased due to the firstsemiconductor layer. By this means, it is possible to effectivelyincrease deposition accuracy of the light emitting semiconductor layerand second semiconductor layer provided on the first semiconductorlayer. Therefore, it is possible to reflect performance as asemiconductor of the first semiconductor layer with few dislocations inthe light emitting semiconductor layer and second semiconductor layer ina state in which cracks are suppressed, and it is possible to obtain thesemiconductor layers (including the first semiconductor layer, lightemitting semiconductor layer and second semiconductor layer, which isthe same in the following description) of light emitting diode structurewith cracks suppressed and high internal quantum efficiency IQE.Further, by the ratio (Hbun/Have) being 300 or less, in addition to theabove-mentioned effects, since it is possible to suppress the warpage ofthe pattern wafer (1) for LEDs, it is possible to increase LED chippingefficiency. From the foregoing, by the ratio (Hbun/Have) meeting thepredetermined range, it is possible to deposit the semiconductor layerswith high internal quantum efficiency IQE and cracks suppressed, and tosuppress the warpage of the pattern wafer (1) for LED with thesemiconductor layers deposited, and it is thereby possible tomanufacture high-efficient LED chips with high production efficiency.Particularly, also when the size of the pattern wafer (1) for LEDs is adiameter of 6 inches or more, it is possible to effectively suppress thewarpage of the epitaxial wafer for LEDs. For this reason, by using thepattern wafer (1) for LEDs of the present invention of the size of6-inches or more, it is possible to thin the thickness of the patternwafer (1) for LEDs, and to effectively suppress the warpage of theepitaxial wafer for LEDs. Particularly, by thinning the thickness of thepattern wafer (1) for LEDs, it is possible to decrease a use amount ofthe pattern wafer for LEDs i.e. increase the environmental suitabilitydegree. Further, it is possible to suppress remaining of heat in thepattern wafer (1) for LEDs, and temperature control is thereby made easyin semiconductor layer deposition.

In the epitaxial wafer for LEDs according to this Embodiment, the firstsemiconductor layer contains an undoped first semiconductor layer anddoped first semiconductor layer sequentially layered from the patternwafer (1) for LEDs side, and it is preferable that a ratio (Hbu/Have) ofa distance (Hbu) between the surface on the light emitting semiconductorlayer side of the pattern wafer (1) for LEDs and a surface on the dopedfirst semiconductor layer side of the undoped first semiconductor layerto an average height (Have) of the uneven structure A meets1.5≦Hbu/Have≦200.

According to this configuration, it is possible to efficientlymanufacture the epitaxial wafer for LEDs with high internal quantumefficiency IQE and cracks suppressed. By the uneven structure A providedon the main surface of the pattern wafer (1) for LEDs, from theprinciples as described already, it is possible to increasecrystallinity of the undoped first semiconductor layer and suppresscracks. Particularly, since the ratio (Hbu/Have) is 1.5 or more, thedegree of flattening of the uneven structure A is increased due to theundoped first semiconductor layer. By this means, it is possible toeffectively increase deposition accuracy of the doped firstsemiconductor layer, light emitting semiconductor layer and secondsemiconductor layer provided on the undoped first semiconductor layer.Therefore, it is possible to reflect the crystallinity of the undopedfirst semiconductor layer with few dislocations in the doped firstsemiconductor layer, light emitting semiconductor layer and secondsemiconductor layer in a state in which cracks are suppressed, and it ispossible to obtain the epitaxial wafer for LEDs with cracks suppressedand high internal quantum efficiency IQE, while reducing the productiontime. Further, by the ratio (Hbu/Have) being 200 or less, in addition tothe above-mentioned effects, since it is possible to suppress thewarpage of the pattern wafer (1) for LEDs, it is possible to enhance LEDchipping efficiency. From the foregoing, by the ratio (Hbu/Have) meetingthe predetermined range, it is possible to deposit the semiconductorlayers with high internal quantum efficiency IQE and cracks suppressed,and to suppress the warpage of the pattern wafer (1) for LED with thesemiconductor layers deposited, and it is thereby possible tomanufacture high-efficient LED chips with high production efficiency.Particularly, also when the size of the pattern wafer (1) for LEDs is adiameter of 6 inches or more, it is possible to effectively suppress thewarpage of the epitaxial wafer for LEDs. For this reason, by using thepattern wafer (1) for LEDs of the present invention of the size of6-inches or more, it is possible to thin the thickness of the patternwafer (1) for LEDs, and to effectively suppress the warpage of theepitaxial wafer for LEDs. Particularly, by thinning the thickness of thepattern wafer (1) for LEDs, it is possible to decrease a use amount ofthe pattern wafer for LEDs i.e. increase the environmental suitabilitydegree. Further, it is possible to suppress remaining of heat in thepattern wafer (1) for LEDs, and temperature control is thereby made easyin semiconductor layer deposition.

In the epitaxial wafer for LEDs according to this Embodiment, the firstsemiconductor layer, the light emitting semiconductor layer and thesecond semiconductor layer may be group III-V-based semiconductors.Further, in the epitaxial wafer for LEDs according to this Embodiment,the first semiconductor layer, the light emitting semiconductor layerand the second semiconductor layer may be GaN-based semiconductors.

A method of manufacturing the epitaxial wafer for LEDs according to thisEmbodiment is characterized by including the step of preparing thepattern wafer (1) for LEDs, the step of performing an optical inspectionon the prepared pattern wafer (1) for LEDs, and the step ofmanufacturing the epitaxial wafer for LEDs as described above using thepattern wafer (1) for LEDs subjected to the optical inspection.

According to this configuration, it is possible to measure the rotationshift angle Θ of the arrangement axis A of the uneven structure A, andit is thereby possible to predict light emitting diode characteristicsof an epitaxial wafer for LEDs to screen without manufacturing theepitaxial wafer for LEDs. Therefore, it is possible to increase yield inmanufacturing of the epitaxial wafer for LEDs.

In the method of manufacturing the epitaxial wafer for LEDs according tothis Embodiment, it is preferable that the step of preparing the patternwafer (1) for LEDs is performed so as to meet the rotation shift angle Θby a transfer method using a mold provided on its surface with a finepattern.

By adopting the transfer method to prepare the uneven structure A,without using excessive apparatus and control mechanism, it is possibleto manufacture the pattern wafer (1) for LEDs meeting the range of therotation shift angle Θ as described above. Particularly, by adopting thetransfer method, it is possible to manufacture efficiently the patternwafer (1) for LEDs having a diameter of 6 inches or more, which is hardto manufacture, with high accuracy.

The pattern wafer (1) for LEDs, epitaxial wafer for LEDs andmanufacturing method thereof according to this Embodiment willspecifically be described below in this order.

<<Pattern Wafer (1) for LEDs>>

The pattern wafer for LEDs according to this Embodiment includes boththe pattern wafer (1) for LEDs which enables a semiconductor layer ofhigh quality with cracks suppressed to be deposited and particularlyenables the internal quantum efficiency IQE to be increased, and apattern wafer (2) for LEDs obtained by providing the pattern wafer (1)for LEDs with high light extraction efficiency LEE as a furtherfunction. In the following description, starting with the description ofthe pattern wafer (1) for LEDs, for the description of the pattern wafer(2) for LEDs, the description will be given mainly with attentiondirected toward further added elements.

The pattern wafer (1) for LEDs according to this Embodiment is providedon its surface with the uneven structure A. The uneven structure A maybe obtained by processing one main surface of the wafer for LEDs or maybe provided on one main surface of the wafer for LEDs separately. Inother words, materials constituting the wafer for LEDs may be the sameas or different from materials constituting the uneven structure A.Herein, the uneven structure A substantially has an arrangement withn-fold symmetry, and is characterized in that the arrangement axis Adirection of the uneven structure A and the crystal axis direction inthe plane of the wafer for LEDs are shifted within a predeterminedrange. The shift amount is referred to as the rotation shift angle Θ.

<Rotation Shift Angle Θ>

The rotation shift angle Θ will be described first. In addition, thearrangement axis A of the uneven structure A and the crystal axis of thepattern wafer (1) for LEDs will be described later. The rotation shiftangle Θ is defined as a minimum rotation angle of the arrangement axis Ain using the crystal axis as a reference. FIG. 1 contains schematicdiagrams to explain the rotation shift angle Θ made by the crystal axisof the pattern wafer (1) for LEDs and the arrangement axis A of theuneven structure A according to this Embodiment. In FIG. 1A, tosimplify, only one axis is shown as each of the arrangement axis A(shown by AXa in FIG. 1A) and the crystal axis (shown by AXc in FIG.1A). As shown in FIG. 1A, assuming that an intersection point of thecrystal axis AXc and the arrangement axis AXa is a center point, therotation shift angle Θ is a minimum angle in rotating the crystal axisAXc until the axis AXc overlaps the arrangement axis AXa.

Using FIG. 1B, the case of considering pluralities of crystal axes andarrangement axes A will be described next. For convenience indescription, FIG. 1B is the case of extracting and drawing three crystalaxes (shown by AXc1, AXc2 and AXc3 in FIG. 1B) and three arrangementaxes A (shown by AXa1, AXa2 and AXa3 in FIG. 1B). For example, the caseis a case of providing the uneven structure A having an arrangement with6-fold symmetry on a wafer for LEDs having crystal axes with 6-foldsymmetry. In such a case, one crystal axis is first selected. Forexample, it is assumed that the crystal axis AXc1 is selected. Next, thecrystal axis AXc1 is rotated to record an angle at which the axis AXc1overlaps the arrangement axis A. For example, a small angle inoverlapping the arrangement axis AXa3 is an angle ΘA, and a small anglein overlapping the arrangement axis AXa1 is an angle ΘB. Among theangles, the minimum angle is the rotation shift angle Θ. In addition,the above-mentioned definition holds in inverting the arrangement axis Aand the crystal axis. In other words, the angle is similarly defined asa minimum angle in rotating the arrangement axis A until the axis Aoverlaps the crystal axis.

<Arrangement Axis>

The arrangement axis A will be described next. The arrangement axis A isan axis to determine an arrangement direction of the uneven structure A.The arrangement of the uneven structure Ahas substantial n-foldsymmetry. In addition, “n-fold symmetry” in the present descriptionmeans “rotational symmetry”. Therefore, n is a positive integer of 2 ormore. By observing the uneven structure A from its surface, for example,using a scanning electron microscope or atomic force microscope, it ispossible to check the arrangement of the uneven structure A.Accordingly, the arrangement axis A has the property of overlapping thesame or different arrangement axis A by rotation of (360/n)°. Herein,the arrangement axis A is defined independently in the case where n inn-fold symmetry is 2 and in the case where n in n-fold symmetry is 3 ormore.

First, in the case of 2-fold symmetry, the arrangement is a symmetricarrangement against some axis. At this point, the arrangement axis A isdefined as an axis in a direction perpendicular to the some axis. Forexample, in the case of the uneven structure A where a plurality ofmutually parallel lines is disposed, the structure is 2-fold symmetryagainst a line segment perpendicular to the lines. Therefore, thearrangement axis A is a line segment parallel to the lines. Further, inthe case of arrangements where an regular-tetragonal arrangement orregular-hexagonal arrangement is drawn in a one-axis direction, andarrangements where an regular-tetragonal arrangement orregular-hexagonal arrangement is modulated in a one-axis directionperiodically (for example, multiplying by a sine curve), thearrangements are 2-fold symmetry in the direction perpendicular to thedraw direction or the modulation direction, and therefore, thearrangement axis A is a line segment perpendicular to the draw directionor the modulation direction. Furthermore, in the case where intervalsamong a plurality of lines are modulated periodically (for example,multiplying by a sine curve), the case is 2-fold symmetry, and a linesegment in a direction parallel to a plurality of lines is thearrangement axis A. Still furthermore, in the case of arrangements wherean regular-tetragonal arrangement or regular-hexagonal arrangement isdrawn in mutually perpendicular two-axis directions at different drawrates in the respective axis directions, the arrangements are 2-foldsymmetry in the direction perpendicular to one of the draw directions,and therefore, the arrangement axis A is a line segment parallel to thedraw direction. Moreover, in the case of arrangements where anregular-tetragonal arrangement or regular-hexagonal arrangement ismodulated in mutually perpendicular two-axis directions with differentmodulation periods in the respective axis directions, the arrangementsare 2-fold symmetry in the direction perpendicular to one of themodulation directions, and therefore, the arrangement axis A is a linesegment parallel to the modulation direction.

On the other hand, in the case of an arrangement with 3-fold symmetry ormore, an axis in the closest direction of convex portions or concaveportions of the uneven structure A is defined as the arrangement axis A.Herein, the closest direction is a direction of a line segment joiningcenter portions of closest tops of the convex-portions or centerportions of closest opening parts of the concave-portions. FIG. 2 is aschematic diagram showing an arrangement example of the uneven structureA having 3-fold symmetry or more in the pattern wafer (1) for LEDsaccording to this Embodiment. For example, it is possible to obtain theexample by observing the surface side with the uneven structure A usingthe scanning electron microscope or atomic force microscope. FIG. 2shows the case where the uneven structure A is regular-tetragonalarranged substantially. The regular-tetragonal arrangement is anarrangement with 4-fold symmetry. In other words, in setting some axisarbitrarily, by rotating the axis (360/n)°=(360/4)°, the axis overlapsanother symmetric axis. Herein, the arrangement axis A is the closestdirection of convex portions or concave portions of the uneven structureA. In FIG. 2, for example, centers of convex portions (or concaveportions, the same in the following description) nearest to the convexportion having the center shown by symbol A are as shown by symbols a,b, c and d in FIG. 2. In other words, the arrangement axis AXa is adirection parallel to one of line segment A-a, line segment A-b, linesegment A-c and line segment A-d joining the center A and respectiveother centers.

FIG. 3 is a schematic diagram showing an arrangement example of theuneven structure A having 3-fold symmetry or more in the pattern wafer(1) for LEDs according to this Embodiment. For example, it is possibleto obtain the example by observing the surface side with the unevenstructure A using the scanning electron microscope or atomic forcemicroscope. FIG. 3 shows the case where the uneven structure A isregular-hexagonally arranged substantially. The regular-hexagonalarrangement is an arrangement with 6-fold symmetry. In other words, insetting some axis arbitrarily, by rotating the axis (360/n)°=(360/6)°,the axis overlaps another symmetric axis. Herein, the arrangement axis Ais the closest direction of convex portions or concave portions of theuneven structure A. In FIG. 3, for example, centers of convex portions(or concave portions, the same in the following description) nearest tothe convex portion having the center shown by A are as shown by symbolsa, b, c, d, e and f in FIG. 3. In other words, the arrangement axis AXais a direction parallel to one of line segment A-a, line segment A-b,line segment A-c, line segment A-d, line segment A-e and line segmentA-f joining the center A and respective other centers.

Further, for example, in the 4-fold symmetric arrangement as describedabove, also in the case where intervals of convex portions or concaveportions on mutually perpendicular two axes are modulated periodically(for example, by multiplying a sine curve), the case is the arrangementwith 4-fold symmetry. Further, in the 4-fold symmetric arrangement asdescribed above, in the case where intervals of convex portions orconcave portions on axes of every 60° with respect to some axis arechanged periodically (for example, by multiplying a sine curve), thecase is the arrangement with 6-fold symmetry. Furthermore, for example,in the 6-fold symmetric arrangement as described above, in the casewhere intervals of convex portions or concave portions on mutuallyperpendicular two axes are modulated periodically (for example, bymultiplying a sine curve), the case is the arrangement with 4-foldsymmetry. Still furthermore, in the 6-fold symmetric arrangement asdescribed above, also in the case where intervals of convex portions orconcave portions on axes of every 600 with respect to some axis arechanged periodically (for example, by multiplying a sine curve), thecase is the arrangement with 6-fold symmetry.

As described above, at least one or more arrangement axes exist, and byapplying the definition as described already, it is possible to obtainthe rotation shift angle Θ.

<Crystal Axis>

The crystal axis will be described below. The crystal axis is theclosest direction of lattice points of a crystal lattice in the planeparallel to the main surface of the pattern wafer (1) for LEDs. FIG. 4is a schematic diagram to explain the crystal axis of the crystallattice in the main surface of the pattern wafer (1) for LEDs accordingto this Embodiment. FIG. 4 shows the case where the crystal lattice inthe plane parallel to the main surface of the wafer for LEDs is aregular-hexagonal lattice, and emphasizes by putting marks in latticeintersection points. The crystal axis is the closest direction oflattice points. For example, in FIG. 4, the intersection points nearestto the intersection point shown by symbol A are as shown by symbols a,b, c, d, e and f. In other words, the crystal axis is a directionparallel to one of line segment A-a, line segment A-b, line segment A-c,line segment A-d, line segment A-e and line segment A-f joining theintersection point A and respective other intersection points. Asarrangements of the crystal lattice observed in the plane parallel tothe main surface of the pattern wafer (1) for LEDs, examples thereof area hexagonal arrangement, a tetragonal arrangement, an arrangement wherea hexagonal arrangement is drawn in a one-axis direction, an arrangementwhere a tetragonal arrangement is drawn in a one-axis direction, anarrangement where a hexagonal arrangement is drawn in mutuallyorthogonal two-axis directions, and an arrangement where a tetragonalarrangement is drawn in mutually orthogonal two-axis directions. In anycase of the crystal lattice arrangements, by applying theabove-mentioned definition, the crystal axis of the present descriptionis defined. For example, when the pattern wafer (1) for LEDs is a singlecrystal sapphire and the main surface is c-surface, m-surface orr-surface, the crystal axis is respectively a-axis, c-axis or n-axis.

<Arrangement with n-Fold Symmetry>

The uneven structure A provided on the pattern wafer (1) for LEDssubstantially has an arrangement with n-fold symmetry. Therefore, incase of noting an initial growth stage of a semiconductor layerdeposited on the pattern wafer (1) for LEDs, it is possible to uniformlydisperse nucleation of the semiconductor layer, and to achieve balancewith ununiformity of nucleus growth. Herein, the ununiformity of nucleusgrowth is that the semiconductor layer partially rises due to nucleusgrowth. In other words, it is possible to disperse the partially raisedsemiconductor layer in the nucleus growth stage.

FIG. 5 contains schematic diagrams illustrating surface observationimages when deposition is stopped in the nucleus growth stage indepositing the semiconductor layer on the surface of the pattern wafer(1) for LEDs. In FIGS. 5A and 5B, symbols X represent positions ofsemiconductor layers partially rising in the nucleus growth stage. FIG.5A schematically represents a state in which semiconductor layers Xpartially rising in the nucleus growth stage are dispersed in thepattern wafer (1) for LEDs according to this Embodiment of the presentinvention. On the other hand, FIG. 5B shows the case where the deviationoccurs in semiconductor layers X partially rising in the nucleus growthstage in the pattern wafer (1) for LEDs with the uneven structure A ofan arrangement with low rotational symmetry. In the pattern wafer (1)for LEDs according to this Embodiment of the present invention, sincethe uneven structure A substantially has n-fold symmetry, dispersionproperties are large in the semiconductor layers X partially rising inthe nucleus growth stage. By this means, portions where coalescence(adherence) of growing semiconductor layers occurs are also dispersed.In other words, stress concentration points are dispersed inside thesemiconductor layer, and collision portions of dislocations are alsodispersed. Accordingly, cracks of the semiconductor layer aresuppressed, and the internal quantum efficiency IQE is effectivelyincreased. In addition, the crack referred to as in the presentdescription is a crack of nano-order. Concerning the case where thesemiconductor layer is deposited on the uneven structure A, the case isobserved where the growth of the semiconductor layer is stopped in afacet formation process. At this point, for example, assuming that thefacet has the shape of a polygon typified by a hexagon, when focused ontwo concave portions of adjacent polygons, a crack generated in thedirection orthogonal to the side and the side of the concave portions ofthe polygons is the crack defined in the present application.

As described already, the rotation shift angle Θ is a shift amountbetween the crystal axis and the arrangement axis A in the rotationdirection in the plane parallel to the main surface of the pattern wafer(1) for LEDs. This rotation shift angle Θ meets 0°<Θ≦(180/n)°. Inaddition, “n” is the degree of rotational symmetry of the unevenstructure A forming the arrangement with n-fold symmetry, and is asdescribed already. For example, in the uneven structure A with 6-foldsymmetry, the rotation shift angle Θ exceeds 0° and is 30° or less. Bythe rotation shift angle Θ meeting the range as described above, it ispossible to increase the size of the bottom of the concave-portion ofthe uneven structure A which significantly contributes to initial growthof the semiconductor layer. At the same time, it is possible to decreasethe number of convex portions of the uneven structure A which thesemiconductor layer with a high growth rate passes through. Therefore,initial growth properties of the semiconductor layer are excellent.Then, in the side and the side of formed facets facing each other, theparallelism of the side and the side is excellent, and cracks aresuppressed.

<More Preferable Range of the Rotation Shift Angle Θ>

The more preferable range of the rotation shift angle Θ is conceivableas described below. First, improvements in internal quantum efficiencyIQE and improvements in crack are effective, and it is effective toincrease the frequency of coalescence of growing semiconductor layersand disperse coalescence portions. Further, in the stage prior tocoalescence of semiconductor layers, it is necessary to make thenucleation excellent and also keep the nucleus growth excellent. Inorder to achieve the matters, it is conceivable it is effective toincrease the size of the concave portion of the uneven structure A towhich the nucleus of the semiconductor layer adheres, and decrease thenumber of convex portions of the uneven structure A that thesemiconductor layer crosses in growing. At the same time, it isimportant to increase the parallelism between the side and the side offormed facets.

FIG. 6 is a graph illustrating the relationship among the rotation shiftangle Θ, the size of the bottom of the concave-portion contributing togrowth of the semiconductor layer and the density of convex portionsthat the growing semiconductor layer passes. FIG. 6 shows results ofcalculation of effects of the rotation shift angle Θ exerted on the size(hereinafter, also simply referred to as the size L of the bottom of theconcavo-portion) of the bottom of the concave-portion contributing togrowth of the semiconductor layer and the density (hereinafter, alsosimply referred to as the density D of convex portions) of convexportions that the growing semiconductor layer passes with respect to theuneven structure A with 6-fold symmetry. In FIG. 6, the horizontal axisrepresents the rotation shift angle Θ, the left vertical axis representsthe size L of the bottom of the concave-portion, and the right verticalaxis represents the density D of convex portions. Further, the plot ofblack circles (●) represents the effect on the size L of the bottom ofthe concavo-portion, and the plot of black squares (▪) represents theeffect on the density D of convex portions. Further, in FIG. 6, the sizeL of the bottom of the concave-portion and the density L of convexportions are normalized to be “1” in the case where the rotation shiftangle Θ is 0°.

From FIG. 6, it is understood that the size L of the concave portion ofthe uneven structure A effective in adherence of the nucleus and itsgrowth is increased, as the rotation shift angle Θ is increased.Particularly, it is understood that there is a maximum point when therotation shift angle Θ is increased, and that the size L of the concaveportion is larger in the case where the rotation shift angle Θ ismaximum than in the case where the rotation shift angle Θ is 0°. On theother hand, it is understood that the density D of convex portionsfunctioning adversely on growth of the semiconductor layer andcoalescence of growing semiconductor layers is decreased, as therotation shift angle Θ is increased. Particularly, it is understood thatthere is a minimum point when the rotation shift angle Θ is increased,and that the density D of convex portions is smaller in the case wherethe rotation shift angle Θ is maximum than in the case where therotation shift angle Θ is 0°.

From the foregoing, in order to suppress cracks effectively and increasethe internal quantum efficiency IQE, the rotation shift angle Θ ispreferably 1° or more, more preferably 3° or more, and most preferably5° or more. In this case, particularly, since the density D of convexportions significantly decreases, the growth properties of thesemiconductor layer are stabilized, and the effect of crack suppressionis large. Further, the rotation shift angle Θ is preferably 7.5° ormore, more preferably 10° or more, and most preferably 14° or more. Inthis case, it is possible to increase the size of the concave portion ofthe uneven structure A effective in adherence of the nucleus and itsgrowth, while holding the above-mentioned crack suppression effect, andit is thereby possible to more improve the internal quantum efficiencyIQE. On the other hand, when the rotation shift angle Θ is (180/n)°, itis conceivable that the direction conversion amount of stress is maximumwhich is capable of being changed by a shift amount between the crystalaxis and the arrangement axis A, the effect of rotating and connectingthe relaxed stress in a vector manner is the highest due to the unevenstructure A with n-fold, the stress relaxation effect is furtherincreased, and that in association therewith, reductions in the warpageare more remarkable.

When the rotation shift angle Θ further meets the following relationshipwith the convex portion of the uneven structure A, the crack suppressioneffect and internal quantum efficiency IQE increasing effect are moreincreased. In using Duty that is a ratio (Φave/Pave) of the averagediameter (Φave) of the bottom of the convex-portion of the unevenstructure A to the average interval Pave, it is preferable that therotation shift angle Θ meets a range of a tan(Duty/2) °≦Θ≦(180/n)°. Inaddition, the average diameter (Φave), average interval (Pave) and Dutywill be described later.

In this case, the effect of internal quantum efficiency IQE improvementand the crack suppression effect on the semiconductor layer are bothmore increased. By the rotation shift angle Θ meeting theabove-mentioned range, the size L of the bottom of the concave-portionsignificantly contributing to initial growth of the semiconductor layeris capable of being made large in the direction approximatelyperpendicular to the growth direction of the semiconductor layer in theplane of the pattern wafer (1) for LEDs, and the size of the surfacewith a fast growth rate of the semiconductor layer is increased. By thismeans, in the case of noting coalescence of growing semiconductorlayers, the interface area of coalescing semiconductor layers isincreased. Further, it is possible to decrease the number of convexportions of the uneven structure which the surface with a fast growthrate of the semiconductor layer passes through, and therefore,coalescence properties of growing semiconductor layers are madeexcellent. From the foregoing, the internal quantum efficiency IQE ismore increased, and cracks occurring in the semiconductor layer areeffectively suppressed.

The relationship between the above-mentioned Duty and the rotation shiftangle Θ was obtained by considering as described below. First, forimprovements in internal quantum efficiency IQE and improvements incrack, it is effective to increase the frequency of coalescence ofgrowing semiconductor layers and disperse coalescence portions. Further,in the stage prior to coalescence of semiconductor layers, it isnecessary to make nucleus growth of the semiconductor layer excellentand also keep nucleus growth properties excellent. In order to achievethe matters, it is conceivable it is effective to increase the size ofthe concave portion of the uneven structure A to which the nucleus ofthe semiconductor layer adheres, and decrease the number of convexportions of the uneven structure A that the semiconductor layer crossesin growing.

FIG. 7 is a graph illustrating the relationship among the Duty, the sizeof the bottom of the concave-portion contributing to growth of thesemiconductor layer, and the density of convex portions that the growingsemiconductor layer passes. FIG. 7 shows results of calculation ofeffects of the Duty exerted on the size L of the bottom of theconcavo-portion and the density D of convex portions, using the case ofthe uneven structure A with 6-fold symmetry as an example. In FIG. 7,the horizontal axis represents the Duty, the left vertical axisrepresents the size L of the bottom of the concave-portion, and theright vertical axis represents the density D of convex portions.Further, the plot of black circles (●) represents the effect on the sizeL of the bottom of the concavo-portion, and the plot of black squares(▪) represents the effect on the density D of convex portions. Further,in FIG. 7, the size L of the bottom of the concave-portion and thedensity D of convex portions are normalized to be “1” in the case wherethe Duty is “0” i.e. there is no uneven structure A.

From FIG. 7, it is understood that the size L of the concave portion ofthe uneven structure A effective in adherence of the nucleus and itsgrowth is increased, as the Duty is increased. On the other hand, it isunderstood that the density D of convex portions functioning-adverselyon growth of the semiconductor layer and coalescence of semiconductorlayers is decreased, as the Duty is increased.

Herein, in FIGS. 6 and 7, the parameters of the horizontal axis are onlydifferent, and similar are behaviors of the effect on the size L of thebottom of the concave-portion and the effect on the density D of convexportions. From this relationship, by obtaining the relationship betweenthe rotation shift angle Θ and the Duty which are represented byrespective horizontal axes in FIGS. 6 and 7, rotation shift angle Θ=atan(Duty/2)° is obtained. Herein, as described already, as the Duty isincreased, since adherence of the nucleus of the semiconductor layer,growth and coalescence effectively occurs, the rotation shift angle Θ isgiven as Θ≧a tan(Duty/2)°.

In other words, in the case of determining the Duty of the unevenstructure A, when the rotation shift angle Θ has a certain value or moreand is in the range of (180/n)° or less, as described above, sinceadherence of the nucleus of the semiconductor layer, growth andcoalescence of growing semiconductor layers is made more excellent, itis possible to obtain an epitaxial wafer for LEDs high in internalquantum efficiency IQE with cracks suppressed. FIG. 8 is a graphillustrating the relationship between the rotation shift angle Θ and theDuty shown in FIGS. 6 and 7. For example, in using the case where theuneven structure A is 6-fold symmetry as an example, the range shown byoblique lines is the most preferable range of the rotation shift angleΘ. In FIG. 8, the horizontal axis represents the Duty, and the verticalaxis represents the rotation shift angle Θ. The plot in FIG. 8represents a tan(Duty/2)°, and the portion higher than the curve in thevertical axis direction is the most preferable range of the rotationshift angle Θ.

In addition, when the size L of the bottom portion of the concaveportion of the uneven structure A is too small, since nucleation of thesemiconductor layer is inhibited, growth of the semiconductor layer isinhibited. It is possible to represent the size of the bottom portion ofthe concave portion of the uneven structure A by using the averageinterval Pave and the Duty. Further, the lower limit value of the sizeof the bottom portion of the concave portion of the uneven structure Ais roughly estimated from the size of the nucleus of the semiconductorlayer. More specifically, with respect to the RAMP process after lowtemperature buffer layer deposition as described later on the patternwafer (1) for LEDs, the travel distance of the nucleus that is dispersedagain inside the RAMP process is approximately 80 nm. From this fact, bysetting the size L of the bottom of the concave-portion at 80 nm ormore, it is possible to suppress the nucleus adhering to the sidesurface of the convex portion, and the crystal quality is increased.From the foregoing, the upper limit value of the Duty is determined, andis calculated as Duty≦1−(Y/Pave). Herein, it is preferable that Y=50 nm,and it is the most preferable that Y=80 nm. In other words, it ispreferable to meet the range of the Duty positioned on the lower side ofthe curve shown in FIG. 9. FIG. 9 is a graph illustrating therelationship between the average interval Pave of the uneven structure Aand the Duty of the pattern wafer (1) for LEDs according to thisEmbodiment. In FIG. 9, the horizontal axis represents the averageinterval Pave of the uneven structure A, and the vertical axisrepresents the Duty. In FIG. 9, the plot of black triangles (▴)represents the preferable case where Y of equation Duty≦1−(Y/Pave) is 50nm, and the plot of black diamonds (♦) represents that Y is 80 nm andrepresents the more preferable case. In addition, with respect to theequation of the Duty as described above, the dimension of the Pave isnanometers.

By the uneven structure A meeting the range of the curve or less shownin FIG. 9, the nucleation of the semiconductor layer is excellent asdescried already. Herein, by meeting the rotation shift angle Θ, thenucleus growth is excellent, the frequency of coalescence of growingsemiconductor layers is high, while it is possible to dispersecoalescence portions, and therefore, it is possible to obtain thesemiconductor layer high in internal quantum efficiency IQE with crackssuppressed.

The crack that is one of the effects of the rotation shift angle Θ asdescribed above will more specifically be described below, includingactual study results. First, a C-surface sapphire of 6-inches was usedas a wafer for LEDs. The main surface of the wafer for LEDs wasprocessed using a nano-fabrication sheet method described later toobtain the pattern wafer (1) for LEDs. Herein, the rotation shift angleΘ was controlled by inclining the nano-fabrication sheet α° from thenormal to bond, using the normal with respect to the Orientation Flat ofthe wafer for LEDs as a reference. In other words, α=Θ. Further, sincethe accuracy resolution of bonding is 1˜2°, the rotation shift angle Θincludes an error of Θ±1°. The arrangement of the uneven structure A wasmade a regular-hexagonal arrangement. In other words, the unevenstructure A is a 6-fold symmetric arrangement. Further, the shape of thetop of the convex-portion of the uneven structure A was checked byscanning electron microscope observation on the cross section of thepattern wafer (1) for LEDs. The result is shown in FIG. 10. FIG. 10A isa scanning electron microscope photograph showing an example of thecross-sectional shape of the top of the convex-portion of the unevenstructure A according to this Embodiment. FIG. 10B is a schematicdiagram indicating a part of FIG. 10A. From FIG. 10, it is understoodthat a flat tabletop did not exist in the top of the convex-portion, andthat the cross-sectional shape of the top of the convex-portion isformed so that curves of the convexity mutually crosses slightly upward.

A low temperature buffer layer with 10 nm was deposited on the preparedpattern wafer (1) for LEDs. Next, gallium nitride was deposited as anundoped first semiconductor layer described later to form facets. In astate during the facet formation, the resultant was removed from achamber, and the gallium nitride deposition surface was observed withthe scanning electron microscope. The result is shown in FIG. 11. FIG.11 is a scanning electron microscope photograph showing an example ofthe undoped first semiconductor layer according to this Embodiment. FIG.11 is a 2500-times observation image. From FIG. 11, it is understoodthat a plurality of facets was formed and that connection of galliumnitride layers was random. Herein, FIG. 12 shows images obtained byenlarging and extracting cracks observed inside the observation image ofFIG. 11. FIG. 12A contains scanning electron microscope photographsshowing cracks. FIG. 12B contains schematic diagrams indicating apart ofFIG. 12A. From FIG. 12, when focused on a hexagonal opening portion ofgrowing gallium nitride, in the gallium nitride layer in the position inwhich the side and the side of hexagons are opposed, it is understoodthat the crack occurred in the direction perpendicular to the sides. Thecrack in the present description refers to such a crack of nanoscale.

As a result of measuring the number of cracks from the scanning electronmicroscope image and quantifying, as the rotation shift angle Θ changedto 0°, 2°, 7.5°, 15°, 22.5° and 30°, the crack density changed to 72×10⁹cracks/cm², 70×10⁹ cracks/cm², 57×10⁹ cracks/cm², 51×10⁹ cracks/cm²,43×10⁹ cracks/cm² and 41×10⁹ cracks/cm². In other words, it isunderstood that the crack density decreased as the rotation shift angleΘ increased. Further, by comparing the decrease degrees, it isunderstood that decreases in the crack density were remarkable in aregion in which the rotation shift angle Θ exceeded 2°. As the reason,control of the rotation shift angle Θ is about ±1°, and it isconceivable that slight rotation of the uneven structure A of 1˜2° isembedded in the error of deposition control in terms of gallium nitridedeposition.

Checked next was the effect on the semiconductor layer due to decreasesin the crack. The undoped first semiconductor layer was furtherdeposited on the sample subjected to the above-mentioned measurement ofcracks to flatten the surface of the gallium nitride layer. In thisstate, the in-plane X-ray rocking curve method was applied to obtain therocking curve, and the Full Width Half Maximum (FWHM) thereof wasevaluated. The result is shown in FIG. 13. FIG. 13 is graph illustratingthe relationship between the crack density and the Full Width HalfMaximum (FWHM) of the rocking curve. Concerning FIG. 13, the horizontalaxis represents the crack density, and the vertical axis represents theFull Width Half Maximum (FWHM) of the rocking curve. From FIG. 13, it isunderstood that the FWHM decreases to 673, 671, 644, 630, 600 and 590,as the crack density decreases to 102×10⁹ cracks/cm², 71×10⁹ cracks/cm²,56×10⁹ cracks/cm², 52×10⁹ cracks/cm², 44×10⁹ cracks/cm² and 40×10⁹cracks/cm². Particularly, it was understood that the numeric value ofFWHM effectively decreases in a region in which the crack density is70×10⁹ cracks/cm² or less. In other words, it was understood thatcrystal uniformity of the semiconductor layer is increased, as the crackdensity decreases, particularly, when the crack density is 70×10⁹cracks/cm² or less.

Further, an n-type gallium nitride layer was deposited on the sampleused in the above-mentioned measurement of rocking curve, as a dopedfirst semiconductor layer. The cathode luminescence (CL) evaluation wasmade to the sample. Herein, CL is techniques for evaluating lightoccurring by applying an electron beam, is the evaluation thatcorresponds to transition from near the bottom of the conduction band tonear the top of the valence band, and therefore, is techniques forevaluating crystal information such as crystal defect, carrierconcentration, stress and impurity. The result is shown in FIG. 14. FIG.14 is a graph illustrating the relationship between the crack densityand a dark spot density obtained from the image obtained by the cathodeluminescence (CL) evaluation. Concerning FIG. 14, the horizontal axisrepresents the crack density, and the vertical axis represents the darkspot density obtained from the image obtained by CL. From FIG. 14, it isunderstood that the CL dark spot density decreases to 5.51×10⁸/cm²,5.52×10⁸/cm², 4.89×10⁸/cm², 4.44×10⁸/cm² and 4.34×10⁸/cm², as the crackdensity decreases to 102×10⁹ cracks/cm², 71×10⁹ cracks/cm², 52×10⁹cracks/cm², 44×10⁹ cracks/cm² and 40×10⁹ cracks/cm². Particularly, itwas understood that the numeric value of the CL dark spot densityeffectively decreases in a region in which the crack density is 71×10⁹cracks/cm² or less. In other words, it was understood that the crystalequality is significantly increased when the crack density is 70×10⁹cracks/cm² or less.

From the foregoing, by making the rotation shift angle Θ exceed 0° andpreferably exceed 2°, it is possible to effectively decrease the crackdensity. By this means, crystal uniformity of the undoped firstsemiconductor layer is effectively increased. Further, it is possible toincrease the crystal quality of the doped first semiconductor layer.Since these increases in the crystal uniformity and crystal quality arefactors to increase the internal quantum efficiency IQE, and areconsidered also factors to increase long-term reliability of thesemiconductor light emitting device, by controlling the crack densitywith the rotation shift angle Θ, it is estimated that it is possible toconcurrently improve light emission performance and long-termreliability of the semiconductor light emitting device.

In addition, tendencies similar to the above-mentioned results wereobtained with respect to shapes of the top of the convex-portion asshown in FIG. 15, although the absolute value of the numeric valueslightly changed. FIG. 15 contains scanning electron microscopephotographs showing examples of the cross-sectional shape of the top ofthe convex-portion of the uneven structure A according to thisEmbodiment. The scanning electron microscope images as shown in FIG. 15are observation images on the cross section of the pattern wafer (1) forLEDs. From FIG. 15, it is understood that the shape of the top of theconvex-portion used in the study includes from the shape of a lens tothe shape that curves of the convex portion mutually cross slightlyupward to form the cross-sectional shape of the vertex portion. From thefact, by adopting the top of the convex-portion that is a corner portionwith a radius of curvature exceeding “0”, it is conceivable that it ispossible to develop the above-mentioned effects of the rotation shiftangle Θ.

It is already described that it is important that the top of theconvex-portion of the uneven structure A is a corner portion with aradius of curvature exceeding “0”. Herein, also in the case where a flatportion exists in the top of the convex-portion i.e. case of tabletopstructure, it was suggested that it is possible to inhibit demerits ofthe tabletop structure by combining with the rotation shift angle Θ.First, the demerits of the tabletop structure are that it is difficultto reduce dislocations due to the semiconductor layer growing from thetabletop. In other words, it is hard to reduce the dislocation densityof the semiconductor layer, and there is a tendency to reduce theinternal quantum efficiency IQE. Herein, although the mechanism is notcertain, it was understood that there is a tendency to enable thereduction amount of the internal quantum efficiency IQE due to thetabletop to be decreased in a range in which the rotation shift angle Θexceeds 10° and is (180/n)° or less. In other words, the reductiondegree of the internal quantum efficiency IQE is decreased. On the otherhand, in the case of the tabletop structure, light scattering propertieswith respect to the emitted light are more increased due to the largearea of the convex portion, and therefore, it is possible to moreincrease the light extraction efficiency LEE. As a result, it wasunderstood that it is possible to manufacture LEDs with high efficiencyby using the pattern wafer (1) for LEDs including the uneven structure Ain which the shape of the top of the convex-portion is the tabletopshape and the rotation shift angle Θ exceeds 10° and is (180/n)° orless. This result was remarkable in a region in which the rotation shiftangle Θ was 15° or more and (180/n)° or less. Further, as the size ofthe tabletop, samples of 20 nm, 50 nm, 100 nm, 300 nm and 500 nm weretested, and it was understood that the cases of 300 nm and 500 nmprovide approximately the same efficiency, and that the performance ismore enhanced in a region of 100 nm or less. It is presumed to be causedby the fact that the re-diffusion distance of the nucleus in the RAMPprocess is about 80 nm after depositing the low temperature bufferlayer. From the foregoing, it was suggested that any contradiction doesnot arise when the corner portion with a radius of curvature exceeding“0” referred to in the present description includes the case where thesize of the tabletop is 100 nm or less. From the foregoing, it ispossible to manufacture high-efficient LEDs with ease, by using thepattern wafer (1) for LEDs in which the convex portion of the unevenstructure A is formed of the corner portion with a radius of curvatureexceeding “0” including the case where the size of the tabletop is 100nm or less, and the rotation shift angle Θ exceeds 10° and is (180/n)°or less and preferably meets a range of 150 to (180/n)°.

From the foregoing, it is possible to reduce cracks in the semiconductorlayer by controlling the shape of the top of the convex-portion of theuneven structure A and the rotation shift angle Θ. Then, it is possibleto enhance the internal quantum efficiency IQE and improve lightemission characteristics of the semiconductor light emitting device.Further, it is possible to improve the long-term reliability of thesemiconductor light emitting device. Herein, when the light extractionefficiency LEE that is another significant problem of the LED is capableof being also increased by uneven structure A, it is possible to moreincrease the external quantum efficiency EQE of the LED. The reason whythe light extraction efficiency LEE of the LED is kept low is that thesemiconductor layer with a high refractive index is sandwiched betweenmedia with relatively low refractive indexes. In such a case, the lightis guided inside the medium with a high refractive index. By thiswaveguide, the emitted light is absorbed to be heat and disappearsbefore being extracted to the outside of the LED. In other words, inorder to increase the light extraction efficiency LEE, it is necessaryto disturb the mode of the emitted light subjected to waveguide. Herein,in consideration of effectively disturbing the travelling direction ofthe emitted light to disturb the waveguide mode, and increasing thelight extraction efficiency LEE, it was understood that the Duty needs apredetermined value or more. It was calculated from thethree-dimensional RCWA method and two-dimensional FDTD method. In otherwords, it is preferable to meet Duty (3.47×10⁻⁸)Pave²+Z. Herein, in theorder of Z of 0.5, 0.6 and 0.65, since the number of modes of lightdiffraction and diffraction intensity increases due to the unevenstructure A, the effect of disturbing the waveguide mode is increased,and the light extraction efficiency LEE is also increased. In otherwords, it is preferable to meet the range of the Duty positioned on theside higher than the curve as shown in FIG. 16. In addition, concerningthe above-mentioned equation to determine the Duty to more increase thelight extraction efficiency LEE, the dimension of Pave is nanometers.

FIG. 16 is a diagram of a graph illustrating the relationship betweenthe average interval Pave and the Duty of the uneven structure A of thepattern wafer (1) for LEDs according to this Embodiment. In FIG. 16, thehorizontal axis represents the average interval Pave of the unevenstructure A, and the vertical axis represents the Duty. In FIG. 16, theplot of black triangles (▴) represents the preferable case where Z inequation Duty≧(3.47×10⁻⁸) Pave²+Z is 0.5, the plot of black diamonds (♦)represents the more preferable case where Z is 0.6, and the plot ofblack circles (●) represents the most preferable case where Z is 0.65.

By the uneven structure A meeting the range of the curve or more asshown in FIG. 16, the intensity of light diffraction and the number ofmodes is increased as described above, and the light extractionefficiency LEE is increased.

When the uneven structure A meets the range of the rotation shift angleΘ as described above, and further meets the relationship between theaverage interval Pave and the Duty as shown in FIG. 17, it is possibleto manufacture the semiconductor layer high in internal quantumefficiency IQE with cracks suppressed, and therefore, the efficiency oflight emission itself is increased. Further, at the same time, the lightemitted efficiently is extracted to the outside of the LED by improvedlight extraction efficiency LEE, and therefore, the external quantumefficiency EQE is increased. In other words, it is possible tomanufacture LED chips high in external quantum efficiency with lowdefect efficiency. Further, since the crack density of the semiconductorlayer inside the LED chip is also reduced, life is increased.

FIG. 17 is a graph illustrating the relationship between the averageinterval Pave and the Duty of the uneven structure A of the patternwafer (1) for LEDs according to this Embodiment. In FIG. 17, thehorizontal axis represents the average interval Pave of the unevenstructure A, and the vertical axis represents the Duty. Plots of blacktriangles (▴), black diamonds (♦) and black circles (●) are curvesdetermined by increases in light extraction efficiency LEE, andrepresent cases where Z of the equation expressed byDuty≧(3.47×10⁻⁸)Pave²+Z described already is 0.5, 0.6 and 0.65,respectively. On the other hand, plots of stars (asterisks) and blacksquares (▪) are curves determined from the viewpoints of the internalquantum efficiency IQE and crack, and in the plots, Y of the equationexpressed by Duty≦1−(Y/Pave) described already is 50 nm and 80 nm,respectively. In other words, when the uneven structure A meets therange of 1−(Y/Pave)≧Duty≧(3.47×10⁻⁸) Pave²+Z, it is possible to developthe effect of enabling semiconductor light emitting devices with highefficiency and long life to be manufactured with low defect efficiencyas described above.

<Uneven Structure A>

The uneven structure A will be described next. The convex portion of theuneven structure A is formed of the corner portion with a radius ofcurvature of the top of the convex-portion exceeding “0”. Herein, thecorner portion with a radius of curvature exceeding “0” means that thetop of the convex portion is formed of a curved surface. Examplesthereof are a cone-shaped body with the front end rounded, lens-shapedbody, dome-shaped body, cone-shaped body and shell-shaped body, andinclude the shapes as shown in FIG. 15.

Thus, when the top of the convex-portion is formed of the corner portionwith a radius of curvature exceeding “0”, it is possible to concurrentlyachieve improvements in internal quantum efficiency IQE and suppressionof cracks. Further, in depositing a semiconductor layer on the unevenstructure A, it is possible to grow the semiconductor layerpreferentially from the bottom of the concave-portion of the unevenstructure A. In other words, it is possible to suppress growth of thesemiconductor layer from the top of the convex-portion of the unevenstructure A. That is, it is possible to prepare initial conditions foradherence of the nucleus of the semiconductor layer to the concaveportion of the uneven structure, growth and coalescence of growingsemiconductor layers.

Herein, by the uneven structure A meeting the rotation shift angle Θ asdescribed already, since it is possible to grow the semiconductor layerpreferentially from the concave portion of the uneven structure A andeffectively carry out coalescence of growing semiconductor layers in adispersed manner, dislocations are reduced, and it is possible tosuppress cracks. The effects are remarkable by meeting the relationshipbetween the rotation shift angle Θ and the Duty descried using FIG. 8.Further, the effects are more remarkable by meeting the relationshipbetween the Duty and the average interval Pave described using FIG. 9.Furthermore, it is possible to concurrently increase the lightextraction efficiency LEE also by meeting the relationship between theaverage interval Pave and the Duty described using FIG. 16.

As described above, by the fact that the range of the rotation shiftangle Θ is met and that the top of the convex-portion of the unevenstructure A is formed of the corner portion with a radius of curvatureexceeding “0”, it is possible to effectively increase the internalquantum efficiency IQE and suppress cracks.

From the viewpoints of excellently developing the effects based on theabove-mentioned principles and making both of improvements in internalquantum efficiency IQE and reductions in the crack excellent, in theconvex portion of the uneven structure A, it is preferable that thediameter is decreased according to the direction from the bottom of theconvex-portion to the top of the convex-portion. By this means,particularly, it is possible to reduce stress occurring from near thevertex portion of the convex portion of the uneven structure A towardthe semiconductor layer. In other words, since it is possible to reducethe stress applied to the growing semiconductor layer from the unevenstructure A, it is possible to decrease residual stress generated insidethe semiconductor layer. By this means, the effect of suppressing cracksis increased in the semiconductor layer.

Further, it is preferable that the side face of the convex-portionconnecting the top of the convex-portion and the bottom of theconcave-portion has tilt angles of two or more stages, and that a radiusof curvature of the point in which the tilt changes exceeds “0” to formacurved surface. In this case, it is possible to provide the stressapplied to the semiconductor layer with a gradient to relax before thestable growth surface of the semiconductor layer comes to the top of theconvex-portion, and therefore, the effect of crack suppression is moreincreased.

Furthermore, in the case where the uneven structure A is comprised of aplurality of independent convex portions and consecutive concaveportion, the above-mentioned effects are further exerted, and therefore,such a case is preferable. In this case, as compared with the case wherethe uneven structure A is comprised of a plurality of independentconcave portions and consecutive convex portion, it is possible torelatively increase the size of the bottom of the concave-portion. Inother words, since it is possible to make the growth properties of thesemiconductor layer from the bottom of the concave-portion as describedalready more excellent, it is possible to improve the internal quantumefficiency IQE and suppress cracks.

Further, by the fact that the flat surface exists in the bottom of theconcave-portion, the effect of increasing the internal quantumefficiency IQE is further increased. This is because it is possible tokeep the growth initial state excellent in the semiconductor layergrowing from the bottom, and it is possible to more exert the effect ofdislocation dispersion properties due to the uneven structure A.

The average interval Pave of the uneven structure (A) is capable ofbeing selected from the viewpoint of balance between the internalquantum efficiency IQE and the light extraction efficiency LEE, andtherefore, is not limited particularly, and for example, theabove-mentioned effects were confirmed by manufacturing pattern wafers(1) for LEDs having uneven structures (A) with 200 nm, 300 nm, 500 nm,700 nm, 1200 nm, 1500 nm, 2500 nm and 5000 nm, respectively. From theviewpoint of effectively increasing the external quantum efficiency EQEof the LED, it is necessary to increase the internal quantum efficiencyIQE. From this viewpoint, it is preferable that the average intervalPave meets 50 nm≦Pave≦1500 nm. When the average interval Pave is 1500 nmor less, since the density of concave portions of the uneven structure Ais increased, it is possible to increase the frequency of coalescence ofgrowing semiconductor layers as described already. In other words, sinceit is possible to increase the frequency with which the dislocationinside the semiconductor layer changes its travelling direction, thedislocation reduction effect is increased, and by this means, theinternal quantum efficiency IQE is effectively increased. On the otherhand, when the average interval Pave is 50 nm or more, it is possible toensure the size of the bottom of the concave-portion of the unevenstructure A significantly contributing to the initial growth of thesemiconductor layer. By this means, it is possible to keep nucleusgrowth of the semiconductor layer excellent in the bottom of theconcave-portion of the uneven structure A. Accordingly, the cracksuppression effect on the semiconductor layer is increased due to thefact that the arrangement axis A of the uneven structure A shifts withina predetermined range by the rotation shift angle Θ. Particularly, fromthe viewpoint of keeping nucleation properties and nucleus growthproperties excellent in the semiconductor layer, the average intervalPave is preferably 100 nm or more, more preferably 200 nm or more, andmost preferably 300 nm or more.

From the viewpoints of increasing the density of concave portions of theuneven structure A, increasing the frequency of coalescence of growingsemiconductor layers, dispersing coalescence portions, effectivelyincreasing the internal quantum efficiency IQE, and decreasing cracks,the average interval is preferably 1200 nm or less, more preferably 1000nm or less, and most preferably 950 nm or less. In addition, by meetingthe relationship between the average interval Pave and the Duty asdescribed already with reference to FIGS. 9, 16 and 17, it is possibleto develop the effect of crack suppression and the effect of improvingthe internal quantum efficiency IQE, and to further increase the lightextraction efficiency LEE also.

<Average Interval (Pave)>

The average interval Pave is assumed to be measured in approximately thesame portions as in samples used in obtaining <Average height (Have) ofthe uneven structure> described in the following <<Semiconductor lightemitting device>>. Alternatively, it is possible to measure in thepattern wafer (1) for LEDs. The average interval Pave of the unevenstructure A is determined according to the following definition,irrespective of the arrangement with n-fold symmetry of the unevenstructure A. An interval P is defined as a distance P_(A1B1) between thecenter of soma convex portion A1 and the center of a convex portion B1most adjacent to the convex portion A1. The average interval (Pave) iscalculated according to the following definition. (1) Arbitrary 10convex portions A1, A2, . . . A10 are selected. (2) An interval P_(AMBM)between a convex portion AM and a convex portion (BM) most adjacent tothe convex portion AM (1≦M≦10) is measured. (3) For the convex portionsA1 to A10, the interval P is measured as in (2). (4) An arithmeticalmean value of intervals P_(A1B1) to P_(A10B10) is defined as the averageinterval (Pave). In addition, the above-mentioned definition is notdependent on n-fold symmetry of the uneven structure A. In other words,the definition is the same in the case where a plurality of convexportions is isolated by the consecutive concave portion, in theline-and-space structure where a plurality of bar-shaped bodies isisolated by a plurality of bar-shaped bodies, and in the arrangement inwhich the ortho-n-gonal arrangement is drawn in a one-axis direction orin two-axis directions. In addition, in the case where a plurality ofconcave portions is separated by the consecutive convex portion, it ispossible to define the average interval (Pave) by replacing the centerof the above-mentioned convex portion with the center of the openingpart of the concave-portion to read. Further, in the case where thelength of the bar-shaped body is extremely long and it is not possibleto observe the end portion with a scanning electron microscope or atomicforce microscope, or the case where the end portion does not exist, thecenter of the convex portion inside these observation images is used asthe center of the above-mentioned convex portion.

<Average Diameter (ΦAve) of the Bottom Portion of the Convex Portion>

The average diameter Φave is assumed to be measured in approximately thesame portions as in the samples used in obtaining <Average height (Have)of the uneven structure> described in the following <<Semiconductorlight emitting device>>. Alternatively, the width is measured in thepattern wafer (1) for LEDs. The average diameter cave of the unevenstructure A is determined according to the following definition,irrespective of the arrangement with n-fold symmetry of the unevenstructure A. A width Φ of the bottom portion of the convex portion isdefined as a distance Φ_(A1) when a distance XY between some point X inthe circumference of the contour and another point Y in thecircumference of the contour is maximum in the contour shape of thebottom portion of some convex portion A1. The average diameter (Φave) iscalculated according to the following definition. (1) Arbitrary 10convex portions A1, A2, . . . A10 are selected. (2) A width Φ_(AM) ofthe bottom portion of the convex portion is measured for the convexportion AM (1≦M≦10). (3) For the convex portions A1 to A10, the width Φof the bottom portion of the convex portion is measured as in (2). (4)An arithmetical mean value of widths Φ_(A1) to Φ_(A10) of the bottomportions of the convex portions is defined as the average diameter(Φave). In addition, in the case where the aspect ratio of the contourshape of the bottom portion of the convex portion is 1.5 or more, thewidth Φ of the bottom portion of the convex portion is defined as theshortest distance between some point X and another point Y in thecircumference of the contour shape of the bottom portion of the convexportion.

<Duty>

The duty is defined as a ratio (Φave/Pave) of the average diameter(Φave) to the average interval (Pave).

<Arrangement of the Uneven Structure A>

The pattern wafer (1) for LEDs according to this Embodiment is providedwith the above-mentioned uneven structure A on a part or the whole ofthe surface of the pattern wafer (1) for LEDs. In addition, furtherdetailed shape arrangement, manufacturing method and materials of theuneven structure A will be described in the following <<Semiconductorlight emitting device>>. In other words, the entire surface of thepattern wafer (1) for LEDs may be covered with the uneven structure A asdescribed above, or the uneven structure A may be provided on a part ofthe surface of the pattern wafer (1) for LEDs. In the followingdescription, the uneven structure A is described as an uneven structureG, and an uneven structure that does not corresponds to the unevenstructure A is described as an uneven structure B.

The pattern wafer (1) for LEDs has the uneven structure G in at least apart thereof. In other words, on the surface of the pattern wafer (1)for LEDs, the entire surface may be covered with the uneven structure G,or a part of the surface may be covered with the uneven structure G.Herein, the region that is not covered with the uneven structure G iscalled the “non-G region” Herein, the non-G region is comprised of theuneven structure B and/or a flat portion. Also in the case where thenon-G region is provided on a part of the surface of the pattern wafer(1) for LEDs, since the already-mentioned effects are developed in theregion covered with the uneven structure G, it is possible to depositthe semiconductor layer high in internal quantum efficiency IQE withcracks suppressed. Further, by meeting the relationship between theaverage interval Pave and the Duty described with reference to FIGS. 16and 17, it is possible to concurrently improve the light extractionefficiency LEE also.

(α) In using the average interval (Pave), it is preferable that theuneven structure G provided on the surface of the pattern wafer (1) forLEDs is provided at least inside a region having an area of10Pave×10Pave because of exhibiting the above-mentioned effects. Inother words, for example, in the pattern wafer (1) for LEDs, it isessential only that the uneven structure G is provided inside the regionof 10Pave×10Pave. In other words, for example, in the case of observingthe surface of the pattern wafer (1) for LEDs using a scanning electronmicroscope or atomic force microscope, it is essential only that theregion having the area of 10Pave×10Pave is formed of the unevenstructure G. Particularly, it is preferable that the total sum of theuneven structure G occupying inside the region having the area of10Pave×10Pave meets the ratio or the size of the uneven structure G asdescribed below. In other words, the inside of the range having the areaof 10Pave×10Pave is comprised of the uneven structure G, and it ispossible to provide a plurality of such ranges. Particularly, by meeting20Pave×20Pave or more, more preferably, 25Pave×25Pave or more, theeffects of adherence of the nucleus of the semiconductor layer, nucleusgrowth and coalescence of growing semiconductor layers are moreremarkable due to the uneven structure G, and therefore, such a range ispreferable. Also in this case, it is preferable that the total sum ofthe uneven structure G meets the ratio or the size of the unevenstructure G as described below. Further, in the case where the regionhaving the area of 50Pave×50Pave, more preferably 75Pave×75Pave iscomprised of the uneven structure G, adherence of the nucleus of thesemiconductor layer, nucleus growth and coalescence of growingsemiconductor layers are excellent also in the non-G region adjacent tothe region covered with the uneven structure G, developed are theeffects of suppressing cracks and improving the internal quantumefficiency IQE, and therefore, such a case is preferable. The effectsare more exerted as the area increases to 100Pave×100Pave or more,150Pave×150Pave or more, and 450Pave×450Pave or more. Also in thesecases, it is preferable that the total sum of the uneven structure Gmeets the ratio or the size of the uneven structure G as describedbelow.

(β) In the case of providing the non-G region in the region covered withthe uneven structure G, it is preferable that the ratio of the non-Gregion is ⅕ or less relative to the uneven structure G. By this means,it is possible to exert the effects of the uneven structure G. From theviewpoint of more exerting the same effects, the ratio is morepreferably 1/10 or less, more preferably 1/25 or less, and mostpreferably 1/50. In addition, by meeting 1/100 or less, it is possibleto more improve the effect of suppressing cracks and improving theinternal quantum efficiency IQE. Particularly, by meeting 1/500 or less,more preferably 1/1,000 or less, uniformity of emitted light output frominside the LED is more improved, and therefore, such a ratio ispreferable. From the same viewpoint, the ratio is preferably 1/10,000 orless, preferably 1/100,000, and preferably 1/1,000,000 or less. Inaddition, the lower limit value is not limited particularly, and as thevalue is lower i.e. approaches zero, the effects of the uneven structureG are more remarkable, being preferable.

(γ) While being dependent on the outside shape and size of the LED chip,when the ratio of the uneven structure G relative to the surface of thepattern wafer (1) for LEDs is 0.002% or more, it is possible to exhibitthe effects as described already in the uneven structure G, andtherefore, such a ratio is preferable. Particularly, by providing thepattern wafer (1) for LEDs with the uneven structure G of 0.02% or more,more preferably 0.2% or more, dispersion properties of dislocations areenhanced inside the semiconductor layer, and therefore, uniformity ofthe internal quantum efficiency IQE is enhanced. Further, sincedispersion properties of coalescence portions of growing semiconductorlayers are enhanced, the effect of suppressing cracks is increased.Furthermore, by the pattern wafer (1) for LEDs including the unevenstructure G of 2.3% or more, more preferably 10% or more, it is possibleto further exert the above-mentioned effects. Still furthermore, in thecase of 20% or more, enhanced is in-plane uniformity of thesemiconductor layer deposited on the pattern wafer (1) for LEDS, theimprovement degree of the internal quantum efficiency IQE is uniformedin the plane of the pattern wafer (1) for LEDs; and the yield ofobtaining high-efficient LED chips is thereby enhanced. From theviewpoint of more exerting the effect, the uneven structure G ispreferably included in a ratio of 30% or more, more preferably in aratio of 40% or more, and most preferably in a ratio of 50% or more.Further, in the case of including the uneven structure G in a ratio of60% or more, propagation properties of the effects of the unevenstructure G to the non-G region are enhanced. In other words, theeffects on adherence of the nucleus of the semiconductor layer, nucleusgrowth and coalescence of growing semiconductor layers due to the unevenstructure G are propagated to the non-G region, and therefore, in thenon-G region, the enhancement degree of the internal quantum efficiencyIQE is increased, while the crack improvement effect is also increased.From the viewpoint of more exerting the effect, the uneven structure Gis preferably included in a ratio of 70% or more, more preferably in aratio of 80% or more, and most preferably in a ratio of 90% or more. Inaddition, in the case where the uneven structure G is included in aratio of 98% or more i.e. the case where the surface of the patternwafer (1) for LEDs is approximately filled with the uneven structure G,growth properties of the semiconductor layer are uniform in the plane ofthe pattern wafer (1) for LEDs, and promoted is uniformity of theenhancement degree of the internal quantum efficiency IQE. In otherwords, characteristic distribution curves are shaper in a plurality ofLED chips manufactured with the epitaxial wafer for LEDs.

(δ) The uneven structure G included in the surface of the pattern wafer(1) for LEDs is preferably 0.0025×10⁻⁶ m² or more. By meeting thisrange, increased is light emission output of the LED chip. This iscapable of being judged from the probability of collision between theemitted light guided inside the LED chip and the uneven structure G,while being dependent on the size and outside shape of the LED chip.Further, in the case of meeting this range, initial growth propertiesare made excellent in the semiconductor layer deposited on the unevenstructure G. In other words, it is possible to decrease velocities ofnucleation and nucleus growth of the semiconductor layer by the unevenstructure G, dislocations are thereby reduced, and the internal quantumefficiency IQE is increased. From the viewpoint of more exerting theabove-mentioned effects, the uneven structure G included in the surfaceof the pattern wafer (1) for LEDs is preferably 0.01×10⁻⁶ m² or more;more preferably 0.04×10⁻⁶ m² or more, and most preferably 0.09×10⁻⁶ m²or more. Further, by the uneven structure G being 0.9×10⁻⁶ m² or more,since in-plane uniformity of the semiconductor layer deposited on thepattern wafer (1) for LEDs is enhanced, the rate at which cracks aresuppressed is increased, and the yield of obtaining the semiconductorlight emitting device is enhanced. From the viewpoint of more exertingthe above-mentioned effects, the uneven structure G is more preferably9×10⁻⁶ m² or more, and most preferably 90×10⁻⁶ m² or more. In addition,when the area is 900×10⁻⁶ m² or more, and more preferably 1.8×10⁻³ m² ormore, propagation properties of the effects of the uneven structure G tothe non-G region are enhanced. In other words, to the non-G region ispropagated the effect of making appropriate adherence of the nucleus ofthe semiconductor layer, nucleus growth and coalescence of growingsemiconductor layers due to the uneven structure G, and therefore, theenhancement degree of the internal quantum efficiency IQE and thereduction degree of cracks are increased also in the non-G region.Particularly, when the area is 3.6×10⁻³ m² or more, and more preferably7.5×10⁻³ m² or more, even in the case of using the outer edge portion ofthe pattern wafer (1) for LEDs, it is possible to obtain excellent LEDs.When one or more uneven structures G meeting the size of the unevenstructure G as described above are provided on the surface of thepattern wafer (1) for LEDs, it is possible to obtain the substrate forLEDs allowed to manufacture high-efficient LED chips with high yield. Inaddition, it is possible to provide a plurality of uneven structures Gmeeting the size of the uneven structure G as described above. In thiscase, at least one of the uneven structures G meets the above-mentionedsize. Particularly, it is preferable that 50% or more of the number ofuneven structures G meets the above-mentioned range of the size, and itis the most preferable that 100% meets the above-mentioned range of thesize.

The arrangement relationship between the uneven structure G and thenon-G region is not limited particularly, as long as the above-mentionedcontent is satisfied, and for example, there are the followingrelationships. As the arrangement relationship between the unevenstructure G and the non-G region, in consideration of the unevenstructure G and non-G region, it is possible to mention arrangements asdescribed below. In addition, the uneven structure G is a set of unevenstructures G meeting one or more of α, β, γ and δ as described abovei.e. the uneven structure G region. Further, as shown in FIG. 18, in thecase where non-G regions 502 are provided inside the uneven structure Gregion 501, as long as the non-G regions 502 meet the ratio described inabove-mentioned β, the shape, regularity and irregularity are notlimited. FIG. 18 contains explanatory diagrams illustrating therelationship between the uneven structure G and the non-G region in thepattern wafer (1) for LEDs according to this Embodiment. In FIGS. 18Aand 18B, a plurality of non-G regions 502 with indefinite contours isarranged inside the uneven structure G region 501. In FIG. 18C, thenon-G region 502 in the shape of a lattice is provided inside the unevenstructure G region 501. Further, in FIG. 18D, a plurality ofsubstantially circular non-G regions 502 is formed inside the unevenstructure G region 501.

The contour shape made by the uneven structure G region 501 is notparticularly limited. In other words, the interface shape between theuneven structure G region 501 and the non-G region 502 is not limited.Therefore, for example, as the interface shape between the unevenstructure G region 501 and the non-G region 502, there are n-gon (n≧3),non-n-gon (n≦3), the shape of a lattice, the shape of a line and thelike. The n-gon may be a regular n-gon or non-regular n-gon.

FIG. 19 contains schematic diagrams illustrating contour shapes formedby the uneven structure G region in the pattern wafer (1) for LEDsaccording to this Embodiment. For example, when a tetragon isrepresented, there are a regular tetragon (square), rectangle,parallelogram, trapezoid, and shapes in which one or more sets ofopposite sides of these tetragons are not parallel. Further, in then-gon (n≧3), the case where n is “4” or more includes the shapes asshown in FIGS. 19A to 19D. FIG. 19A shows a tetragon, FIG. 19B shows ahexagon, FIG. 19C shows an octagon, and FIG. 19D shows a dodecagon. Thenon-n-gon is the n-gon (n≧3) as described above including a structureincluding a corner portion with a radius of curvature exceeding “0”,e.g. circle, ellipse, shape in which the corner of the above-mentionedn-gon as described above is rounded (shape in which a radius ofcurvature of the corner of the above-mentioned n-gon exceeds “0”), orrounded corner (portion with a radius of curvature exceeding “0”).Therefore, for example, the contour shapes include shapes exemplified inFIGS. 19E to 19H. In addition, the contour shapes of the non-G regionare capable of adopting the shapes described as the contour shapes of aset of uneven structures G as described above.

First, there is a state in which the uneven structure G region 501 isenclosed or sandwiched with/between the non-G region(s) 502. FIG. 20contains plan schematic diagrams illustrating states obtained byobserving, from the surface, the pattern wafer (1) for LEDs according tothis Embodiment. FIGS. 20A to 20F show states in which the unevenstructure G region 501 is enclosed with the non-G region 502. As shownin FIG. 20A, the uneven structure G region 501 is provided on thesurface of the pattern wafer (1) 500 for LEDs, and the outer region maybe comprised of the non-G region 502. It is preferable that the unevenstructure G region 501 meets the above-mentioned ratio. Further, it ispreferable that the uneven structure G region 501 meets the size asdescribed already. In FIG. 20B or FIG. 20C, a plurality of unevenstructure G regions 501 is arranged on the surface of the pattern wafer(1) 500 for LEDs while being mutually spaced, and regions between theuneven structure G regions 501 and outside the uneven structure G region501 may be filled with the non-G region 502. In this case, it ispreferable that the above-mentioned ratio is met relative to the totalarea of the uneven structure G. Further, it is preferable that at leastone uneven structure G meets the size as described already, and it ismore preferable that all uneven structures G meet the size as describedalready. Furthermore, when a plurality of uneven structures G isprovided, the uneven structure G regions 501 may be arranged regularlyas shown in FIG. 20C, or may be arranged irregularly as shown in FIG.20D. As the regular arrangement, there are a tetragonal arrangement,hexagonal arrangement, arrangements in which these arrangements aredrawn in a one-axis direction, arrangements in which these arrangementsare drawn in two-axis directions, and the like. Further, the contourshape of the uneven structure G region 501 is shown in the shape of acircle in FIGS. 20A to 20D, and as shown in FIG. 20E, it is alsopossible to adopt an indefinite shape. For example, as the outside shapeof the uneven structure G region 501, it is possible to mention shapessuch as an n-gon (n≧3), corner-rounded n-gon (n≧3), circle, ellipse, theshape of a line, the shape of a star, the shape of a lattice, and thelike. Furthermore, as shown in FIG. 20F, it is possible to adopt theshape in which the uneven structure G region 501 is enclosed with thenon-G region 502, the outer region is enclosed with the uneven structureG region 501, and further, the outer region is enclosed with the non-Gregion 502. In addition, in FIGS. 20A to 20D, the uneven structure Gregion is described in the shape of a circle, and the contour shapesmade by the uneven structure G region 501 may adopt the shapes asdescribed with reference to FIG. 19.

FIG. 21 contains plan schematic diagrams illustrating states obtained byobserving, from the surface, the pattern wafer (1) for LEDs according tothis Embodiment. FIG. 21 shows the case where the uneven structure Gregion 501 is sandwiched between non-G regions 502. As shown in FIGS.21A and 21B, the uneven structure G region 501 is provided on thesurface of the pattern wafer (1) 500 for LEDs, and the outer regions maybe comprised of the non-G regions 502. It is preferable that the unevenstructure G meets the above-mentioned ratio. Further, it is preferablethat the uneven structure G meets the size as described already. Asshown in FIG. 21C, a plurality of uneven structure G regions 501 isarranged on the surface of the pattern wafer (1) 500 for LEDs whilebeing mutually spaced, and regions between the uneven structure Gregions 501 and outside the uneven structure G region 501 may be filledwith the non-G regions 502. In this case, it is preferable that theabove-mentioned ratio is met relative to the total area of the unevenstructure G. Further, it is preferable that at least one unevenstructure G meets the size as described already, and it is morepreferable that all uneven structures G meet the size as describedalready. Furthermore, as shown in FIG. 21D, it is possible to make anarrangement in which the uneven structure G regions 501 include thenon-G regions 502 and are continuously provided. In this case, it ispreferable that the above-mentioned ratio is met relative to the area ofthe uneven structure G. Still furthermore, it is preferable that theuneven structure G meets the size as described already. Moreover, theinterface shape between the uneven structure G region 501 and the non-Gregion 502 may be linear; or may be bowed as shown in FIG. 21E. As theshape of the uneven structure G region 501, there are the shape of aline, the shape of a lattice, the shape of a mesh and the like. Further,as shown in FIG. 21F, it is possible to adopt the shape in which theuneven structure G region 501 is sandwiched between the non-G regions502, the outer regions are sandwiched between the uneven structure Gregions 501, and further, the outer regions are sandwiched between thenon-G regions 502. In addition, in FIG. 21, the contour line made by theuneven structure G region 501 is described as the shape of a line orsubstantially in the shape of a line, and it is also possible to adoptthe shapes as described with reference to FIG. 19.

In the case where a plurality of uneven structure G regions 501 asdescribed above is provided, the interface shape between each of theuneven structure G regions 501 and the non-G region 502 may be a single,or may differ for each uneven structure G region 501.

Further, in the arrangement relationship between the uneven structure Gregion 501 and the non-G region 502 as described above, both of thecases may coexist i.e. the case where the uneven structure G region 501is enclosed with the non-G region 502 and the case where the unevenstructure G region 501 is sandwiched between the non-G regions 502 maycoexist.

Furthermore, as shown in FIGS. 20F and 21F, when the non-G region. 502is provided outside the first uneven structure G region 501 (G1), thesecond uneven structure G region 501 (G2) is provided outside the region502, and the non-G region 502 is further provided outside the region501, the second uneven structure G region 501 (G2) may be discontiguous.

The non-G region may be comprised of the uneven structure B, may becomprised of a flat portion, or may be comprised of the uneven structureB and flat portion.

Further, in the above-mentioned description, the outside shapes of thepattern wafer (1) 500 for LEDs are all described as rectangles, but theoutside shape of the pattern wafer (1) 500 for LEDs is not limitedthereto, and it is possible to adopt the shape of a circle, the shapeincluding an arc having the curvature of a circle and straight line,n-gon (n≧3), non-n-gon (n≧3), the shape of a lattice, the shape of aline, and the like. The n-gon may be a regular n-gon or non-regularn-gon. For example, when a tetragon is represented, there are a regulartetragon (square), rectangle, parallelogram, trapezoid, and shapes inwhich one or more sets of opposite sides of these tetragons are notparallel. Further, in the n-gon (n≧3), the case where n is “4” or moreincludes the shapes as shown in FIGS. 19A to 19D. FIG. 19A shows atetragon, FIG. 19B shows a hexagon, FIG. 19C shows an octagon, and FIG.19D shows a dodecagon. The non-n-gon is the n-gon (n≧3) as describedabove including a structure without a corner, e.g. circle, ellipse,shape in which the corner of the above-mentioned n-gon as describedabove is rounded (shape in which a radius of curvature of the corner ofthe above-mentioned n-gon exceeds “0”), or rounded corner (cornerportion with a radius of curvature exceeding “0”). Therefore, forexample, the shapes include shapes exemplified in FIGS. 19F to 19H.Among the shapes, it is preferable to adopt a line symmetrical shape.

<<Epitaxial Wafer of LEDs>>

Described next are epitaxial wafers for LEDs using the pattern wafer (1)for LEDs according to this Embodiment.

FIG. 22 is a cross-sectional schematic diagram showing an example of theepitaxial wafer for LEDs according to this Embodiment. As shown in FIG.22, in the epitaxial wafer 100 for LEDs, the pattern wafer (1) 10 forLEDs is provided on its surface with an uneven structure 20. The unevenstructure 20 is the uneven structure A as described above. In otherwords, the arrangement axis A of the uneven structure 20 and the crystalaxis of the pattern wafer (1) 10 for LEDs meet the relationship of therotation shift angle Θ as described above, and the convex portion of theuneven structure 20 is formed of the corner portion with a radius ofcurvature exceeding “0”. A first semiconductor layer 30, light emittingsemiconductor layer 40 and second semiconductor layer 50 that aresemiconductor layers are sequentially layered on the surface includingthe uneven structure 20 of the pattern wafer (1) 10 for LEDs. Herein, inthe LED chip manufactured from the epitaxial wafer 100 for LEDs, emittedlight generated in the light emitting semiconductor layer 40 isextracted from the second semiconductor layer 50 side or the patternwafer (1) 10 for LEDs. Further, the first semiconductor layer 30 and thesecond semiconductor layer 50 are comprised of mutually differentsemiconductor crystals. Herein, it is preferable that the firstsemiconductor layer 30 flattens the uneven structure 20. In this case,since the uneven structure 20 is the uneven structure A, dislocations ofthe first semiconductor layer 30 are reduced, and cracks are suppressed.When the first semiconductor layer 30 is provided so as to flatten theuneven structure 20, since it is possible to reflect performance of thefirst semiconductor layer 30 as a semiconductor layer in the lightemitting semiconductor layer 40 and the second semiconductor layer 50,the internal quantum efficiency IQE is increased, and cracks aresuppressed. In other words, from the principles described in <<Patternwafer (1) for LEDs>>, dislocations of the first semiconductor layer 30are reduced, while it is possible to suppress cracks, it is possible toreflect the performance of the first semiconductor layer 30 havingexcellent crystallinity in the light emitting semiconductor layer 40 andthe second semiconductor layer 50 sequentially, and also afterdepositing the second semiconductor layer 50, it is possible to reducecracks of the semiconductor layer.

Further, as shown in FIG. 23, the first semiconductor layer 30 may becomprised of an undoped first semiconductor layer 31 and doped firstsemiconductor layer 32. FIG. 23 is a cross-sectional schematic diagramshowing another example of the epitaxial wafer for LEDs according tothis Embodiment. In this case, as shown in FIG. 23, in the epitaxialwafer 200 for LEDs, when the pattern wafer (1) 10 for LEDs, undopedfirst semiconductor layer 31 and doped first semiconductor layer 32 arelayered in this order, in addition to improvements in internal quantumefficiency IQE and the effect of reducing cracks, it is possible toshorten the manufacturing time of the epitaxial wafer 200 for LEDs.Herein, when the undoped first semiconductor layer 31 is provided so asto flatten the uneven structure 20, since it is possible to reflectperformance of the undoped first semiconductor layer 31 as asemiconductor in the doped first semiconductor layer 32, the lightemitting semiconductor layer 40 and the second semiconductor layer 50,the internal quantum efficiency IQE is increased, and cracks arereduced. In other words, from the principles described in <<Patternwafer (1) for LEDs>>, it is possible to enhance crystallinity of theundoped first semiconductor layer 31, it is possible to reflect theperformance of the undoped first semiconductor layer 31 having excellentcrystallinity in the doped first semiconductor layer 32, the lightemitting semiconductor layer 40 and the second semiconductor layer 50sequentially, and also after depositing the second semiconductor layer50, it is possible to reduce cracks of the semiconductor layer.

Further, as shown in FIG. 24, the first semiconductor layer 30preferably includes a buffer layer 33. FIG. 24 is a cross-sectionalschematic diagram showing still another example of the epitaxial waferfor LEDs according to this Embodiment. As shown in FIG. 24, in theepitaxial wafer 300 for LEDs, the buffer layer 33 is provided on theuneven structure 20, subsequently the undoped first semiconductor layer31 and doped first semiconductor layer 32 are sequentially layered,nucleation and nucleus growth, which is the initial conditions ofcrystal growth of the first semiconductor layer 30, is thereby madeexcellent, the performance of the first semiconductor layer 30 as asemiconductor is enhanced, and the degree of improvements in internalquantum efficiency IQE is thereby increased. Herein, the buffer layer 33may be disposed to flatten the uneven structure 20, but since a growthrate of the buffer layer 33 is slow, from the viewpoint of shorteningthe manufacturing time of the epitaxial wafer 300 for LEDs, it ispreferable that the uneven structure 20 is flattened with the undopedfirst semiconductor layer 31 provided on the buffer layer 33. When theundoped first semiconductor layer 31 is provided so as to flatten theuneven structure 20, since it is possible to reflect the performance ofthe undoped first semiconductor layer 31 as a semiconductor in the dopedfirst semiconductor layer 32, the light emitting semiconductor-layer 40and the second semiconductor layer 50, the internal quantum efficiencyIQE is increased, and cracks are suppressed. In addition, in FIG. 24,the buffer layer 33 is disposed to cover the surface of the unevenstructure 20, and may also be provided partially on the surface of theuneven structure 20. Particularly, it is possible to provide the bufferlayer 33 preferentially in the bottom of the concave-portion of theuneven structure 20. In this case, since it is possible to carry outadherence of the nucleus preferentially on the bottom of theconcave-portion of the uneven structure 20, subsequent nucleus growthproperties are made excellent, and it is possible to keep coalescence ofgrowing semiconductor layers excellent. In addition, in the case ofusing the pattern wafer (1) 10 for LEDs according to this Embodiment,since it is possible to increase the internal quantum efficiency IQEexcellently, the buffer layer 33 may not be provided.

The epitaxial wafers 100, 200 and 300 for LEDs respectively shown inFIGS. 22 to 44 are of an example of applying the semiconductor layer ofdouble-hetero structure, and the layered structure of the firstsemiconductor layer 30, light emitting semiconductor layer 40 and secondsemiconductor layer 50 is not limited thereto.

FIG. 25 is a cross-sectional schematic diagram illustrating an exampleof an LED chip manufactured from the epitaxial wafers for LEDs as shownin FIGS. 22 to 24. As shown in FIG. 25, in the LED chip 400, it ispossible to provide a transparent conductive layer 60 on the secondsemiconductor layer 50, an anode electrode 70 on the surface of thetransparent conductive layer 60, and a cathode electrode 80 on thesurface of the first semiconductor layer 30. The arrangement of thetransparent conductive layer 60, anode electrode 70 and cathodeelectrode 80 can be optimized as appropriate corresponding to the LEDchip, is thereby not limited, and generally, is provided as exemplifiedin FIG. 25.

Further, in the LED chip 400 as shown in FIG. 25, the uneven structure20 is provided between the pattern wafer (1) 10 for LEDs and the firstsemiconductor layer 30, and as shown in FIG. 26, it is also possible tofurther provide other uneven structures. FIG. 26 is a cross-sectionalschematic diagram showing another example of the LED chip according tothis Embodiment. As shown in FIG. 26, as the uneven structures toseparately provide, there are the following structures.

Uneven structure 601 provided on the surface on the side opposite to thelight emitting semiconductor layer 40 of the pattern wafer (1) 10 forLEDs

Uneven structure 602 provided between the second semiconductor layer 50and the transparent conductive layer 60

Uneven structure 603 provided on the surface of the transparentconductive layer 60

Uneven structure 604 provided between the transparent conductive layer60 and the anode electrode 70

Uneven structure 605 provided between the first semiconductor layer 30and the cathode electrode 80

Uneven structure 606 provided on the surface of the anode electrode 70

Uneven structure 607 provided on the surface of the cathode electrode 80

Uneven structure 608 provided on side surfaces of the firstsemiconductor layer 30, light emitting semiconductor layer 40, secondsemiconductor layer 50 and pattern wafer (1) 10 for LEDs

By further providing at least one uneven structure among the unevenstructures 601 to 608 as well as the uneven structure 20, it is possibleto develop effects corresponding to each of the uneven structure 601 to608 as described below.

By providing the uneven structure 601, the light extraction efficiencyLEE is increased. In the LED chip according to this Embodiment, theinternal quantum efficiency IQE is increased. In other words, it ispossible to produce photos effectively inside the LED chip. Therefore,in the LED chip according to this Embodiment, it is preferable toprovide the uneven structure 601. In addition, instead of providing theuneven structure 601, also by removing the pattern wafer (1) for LEDs,for example, by the laser liftoff method or the like, the lightextraction efficiency LEE is significantly increased similarly.

By providing the uneven structure 602, since it is possible to increasethe light extraction efficiency LEE, the external quantum efficiency EQEis significantly improved. Further, since diffusion properties ofelectrons in the transparent conductive layer 60 are enhanced, it ispossible to increase the size of the LED chip.

By providing the uneven structure 603, it is possible to increase thelight extraction efficiency LEE. In the epitaxial wafer for LEDsaccording to this Embodiment, the internal quantum efficiency IQE isincreased. In other words, it is possible to produce photos effectivelyinside the LED chip. Therefore, in the LED chip according to thisEmbodiment, it is preferable to provide the uneven structure 603.

By providing the uneven structure 604, since it is possible to increasethe contact area between the transparent conductive layer 60 and theanode electrode 70, it is possible to suppress peeling of the anodeelectrode 70. Further, since it is possible to reduce ohmic resistanceand to enhance ohmic contact, it is possible to improve the electroninjection efficiency EIE, and it is possible to increase the externalquantum efficiency EQE. In the epitaxial wafer for LEDs according tothis Embodiment, the internal quantum efficiency IQE is increased. Inother words, it is possible to produce photos effectively inside the LEDchip. Therefore, in the LED chip according to this Embodiment, it ispreferable to provide the uneven structure 604.

By providing the uneven structure 605, since the contact area betweenthe first semiconductor layer 30 and the cathode electrode 80 isincreased, it is possible to suppress peeling of the cathode electrode80.

By providing the uneven structure 606, since the fix strength of wiringconnected to the anode electrode 70 is increased, it is possible tosuppress peeling.

By providing the uneven structure 607, since the fix strength of wiringprovided on the surface of the cathode electrode 80 is increased, it ispossible to suppress peeling.

By providing the uneven structure 608, since it is possible to increaseemission light quantities output from the side surfaces of the firstsemiconductor layer 30, light emitting semiconductor layer 40, secondsemiconductor layer 50 and pattern wafer (1) 10 for LEDs, it is possibleto reduce the rate of emitted light which attenuates and disappears, inthe waveguide mode. Therefore, the light extraction efficiency LEE isincreased, and it is possible to enhance the external quantum efficiencyEQE.

As described above, by using the pattern wafer (1) 10 for LEDs accordingto this Embodiment, it is possible to increase the internal quantumefficiency IQE of the epitaxial wafer for LEDs, and to reduce thewarpage of the epitaxial wafer for LEDs. Therefore, also in the case ofusing large wafers for LEDs with 4-inches or 6-inches, it is possible tomanufacture epitaxial wafers for LEDs with little warpage, and tomanufacture LED chips with low percent defective. Particularly, by usingthe pattern wafer (1) for LEDs with a diameter of 6 inches or more, itis possible to thin the thickness of the pattern wafer (1) for LEDs.Therefore, since environmental suitability is enhanced and heatcontrollability is improved in depositing the semiconductor layer,crystallinity is more enhanced in the semiconductor layer of theepitaxial wafer for LEDs. Further, as described already, since it ispossible to thin the thickness of the semiconductor layer, it ispossible to effectively suppress the warpage of the epitaxial wafer forLEDs. Moreover, by further providing at least one uneven structure ofthe uneven structures 601 to 608 as described above, it is possible todevelop the effects due to the uneven structures 601 to 608.Particularly, from the viewpoint of also improving the light extractionefficiency LEE and achieving high external quantum efficiency, it ispreferable to provide at least one of the uneven structure 601 anduneven structure 603. Further, from the viewpoint of also increasing theelectron injection efficiency EIE, it is preferable to provide theuneven structure 604.

Moreover, the pattern wafer (1) 10 for LEDs may be removed from alayered product in which an electrode is formed on the surface on whichthe second semiconductor layer 50 is exposed in the epitaxial wafers100, 200, 300 for LEDs exemplified in FIG. 22 to 24 as described aboveand a support substrate is disposed on the surface with the electrodeexposed. It is possible to attain removal of the pattern wafer (1) 10for LEDs by liftoff using laser light, and complete dissolution orpartial dissolution of the pattern wafer (1) 10 for LEDs. Particularly,in the case of adopting a silicon wafer as the pattern wafer (1) 10 forLEDs, removal by dissolution is preferable, from the viewpoint ofaccuracy of the surface (hereinafter, referred to as uneven structuresurface) with the uneven structure provided thereon. By thus removingthe pattern wafer (1) 10 for LEDs, it is possible to further increasethe light extraction efficiency LEE more in a state in whichimprovements in internal quantum efficiency IQE are maintained. This isbecause differences in the refractive index are large between thepattern wafer (1) 10 for LEDs and the first semiconductor layer 30, thelight emitting semiconductor layer 40 and the second semiconductor layer50. By removing the pattern wafer 1 (10) for LEDs, it is possible toassemble an LED epitaxial wafer with the first semiconductor layer 30 asa light output surface.

Described next are terms used in the description of elementsconstituting the epitaxial wafers 100, 200 and 300 for LEDs. Inaddition, the following description is also applied to LED chips 400 and500.

<Average Height (Have) of the Uneven Structure>

The height of the uneven structure 20 is given as an arithmetical meanvalue of distances between the top of the convex-portion and the bottomof the concave-portion of the uneven structure. First, a region of asquare of 50 μm×50 μm parallel to the main surface of the pattern wafer(1) 10 for LEDs is made on the uneven structure 20 surface of thepattern wafer (1) 10 for LEDs. In addition, in the case of an epitaxialwafer for LEDs with a semiconductor layer deposited on the pattern wafer(1) 10 for LEDs, the semiconductor layer is removed, and observed is theuneven structure surface of the pattern wafer (1) 10 for LEDs. Next, theregion of a square of 50 μm×50 μm is divided into 25 regions each of asquare of 10 μm×10 μm so as not to overlap mutually. Next, 5 regions areselected arbitrarily from among 25 regions each of a square of 10 μm×10μm existing. Herein, it is assumed that the selected regions each of asquare of 10 μm×10 μm are respectively a region A, region B, region C,region D and region E. Subsequently, the region A is observed with ahigher magnification, and is enlarged so that at least 100 convexportions are sharply observed. Next, 10 convex portions are selectedarbitrarily from the observed convex portions, and a height h of each ofthe convex portions is obtained. Herein, it is possible to judge theheight h of the convex portion by observation with Tilt reflected inscanning electron microscope observation or atomic force microscopeobservation. The arithmetical mean height of 10 convex portions measuredin the region A is defined as ha. The same operation as the region A isperformed on the region B, region C, region D and region E to obtain hb,hc, hd and he, respectively. The average height (Have) of the unevenstructure 20 is given as (ha+hb+hc+hd+he)/5. In addition, theabove-mentioned description is the description in the case where theuneven structure 20 is comprised of a plurality of independent convexportions, and in the case where the uneven structure 20 is comprised ofa plurality of concave portions, the height h of the uneven structure 20is defined by replacing the convex portion as described above with theconcave portion to read. Further, in the case of the epitaxial wafer forLEDs, it is assumed that the term related to the thickness of thesemiconductor layer as described below is first calculated, thesemiconductor layer is then removed, and that the average height (Have)of the uneven structure 20 is obtained. In other words, it is assumedthat the information related to the thickness of the semiconductor layeras described below and the average height (Have) of the uneven structure20 as described above are measured in approximately the same portions inthe same sample. Further, the average interval Pave of the unevenstructure 20 and the average diameter (average diameter) Φave of thebottom portion of the convex portion of the uneven structure 20 areobtained in the same measurement portions in the same sample as thesample used in obtaining the average height (Have) of the unevenstructure.

<Distance Hbun>

A distance Hbun is defined as a distance between the surface on thelight emitting semiconductor layer 40 side of the pattern wafer (1) 10for LEDs and the surface on the light emitting semiconductor layer 40side of the first semiconductor layer 30. Herein, the surface on thelight emitting semiconductor layer 40 side of the pattern wafer (1) 10for LEDs is defined as an average bottom of the concave-portion positionof the uneven structure 20. Further, the surface on the light emittingsemiconductor layer 40 side of the first semiconductor layer 30 isdefined as an average surface. The average is arithmetical mean, and thenumber of average points is determined to “10”. In other words, thedistance Hbun is an average thickness of the first semiconductor layer30 with the average bottom of the concave-portion position of the unevenstructure 20 as a reference. In addition, the above-mentionedarithmetical mean is calculated by observing the cross section of theepitaxial wafer for LEDs. As the observation method, it is possible toadopt transmission electron microscope observation or scanning electronmicroscope observation. Further, the observation range is assumed to bea range in which the number of 5 or more and 20 or less of convexportions (or concave portions) is capable of being observed sharply inthe observation.

<Distance Hbu>

A distance Hbu is defined as a distance between the surface on the lightemitting semiconductor layer 40 side of the pattern wafer (1) 10 forLEDs and the surface on the light emitting semiconductor layer 40 sideof the undoped first semiconductor layer 31. Herein, the surface on thelight emitting semiconductor layer. 40 side of the pattern wafer (1) 10for LEDs is defined as an average bottom of the concave-portion positionof the uneven structure 20. Further, the surface on light emittingsemiconductor layer 40 side of the undoped first semiconductor layer 31is defined as an average surface. The average is arithmetical mean, andthe number of average points is determined to “10”. In other words, thedistance Hbu is an average thickness of the undoped first semiconductorlayer 31 with the average bottom of the concave-portion position of theuneven structure 20 as a reference. In addition, the above-mentionedarithmetical mean is calculated by observing the cross section of theepitaxial wafer for LEDs. As the observation method, it is possible toadopt-transmission electron microscope observation or scanning electronmicroscope observation. Further, the observation range is assumed to bea range in which the number of 5 or more and 20 or less of convexportions (or concave portions) is capable of being observed sharply inthe observation.

Next, each of the elements constituting the epitaxial wafer 100(including 200, 300 and LED chips 400, 600, the same in the followingdescription) will be described in detail.

<The Ratio (Hbun/Have) of the Distance Hbun to the Average Height(Have)>

The ratio (Hbun/Have) of the distance Hbun to the average height (Have)meets 2≦Hbun/Have≦300.

The ratio (Hbun/Have) means the ratio between the average height (Have)of the uneven structure 20 and the average thickness Hbun of the firstsemiconductor layer 30, and as the ratio (Hbun/Have) increases, theaverage thickness Hbun of the first semiconductor layer 30 increases. Inthe case where the ratio (Hbun/Have) is 2 or more, it is possible todevelop the effect of improving the internal quantum efficiency IQE dueto the uneven structure 20, and therefore, such a case is preferable.When the ratio (Hbun/Have) is 2 or more, the degree of flattening theuneven structure A due to the first semiconductor layer 30 is enhancedwith cracks suppressed. By this means, it is possible to effectivelyenhance deposition accuracy of the light emitting semiconductor layer 40and second semiconductor layer 50 provided on the first semiconductorlayer 30. Therefore, it is possible to reflect performance as asemiconductor of the first semiconductor layer 30 with few dislocationsin the light emitting semiconductor layer 40 and second semiconductorlayer 50 in a state in which cracks are suppressed, and it is possibleto obtain epitaxial wafers for LEDs with cracks suppressed and highinternal quantum efficiency IQE. Further, when the ratio (Hbun/Have) is3.5 or more, since flatness of the surface of the first semiconductorlayer 30 is excellent, and in association therewith, film thicknessuniformity is enhanced in the light emitting semiconductor layer 40, andin-plane uniformity of emission wavelengths is enhanced. From theviewpoints of more exerting these effects, the ratio is preferably is5.5 or more, and more preferably 8.0 or more. Particularly, when theratio (Hbun/Have) is 10 or more, it is possible to more decrease theeffect of the top of the convex-portion of the uneven structure 20 onthe surface of the first semiconductor layer 30, and it is therebypossible to achieve more excellent flatness of the surface on the lightemitting semiconductor layer 40 of the first semiconductor layer 30. Inother words, increased is the effect of enhancing the internal quantumefficiency IQE. From the same viewpoint, the (Hbun/Have) is preferably12 or more, more preferably 14 or more, and most preferably 16 or more.Further, from the viewpoints of increasing the probability of collisionbetween dislocations in between the average top of the convex-portionposition of the uneven structure 20 of the first semiconductor layer 30and the light emitting semiconductor layer 40 and more increasing theinternal quantum efficiency IQE, the ratio (Hbun/Have) is morepreferably 20 or more, and most preferably 25 or more. On the otherhand, when the ratio (Hbun/Have) is 300 or less, it is possible tosuppress the warpage of the epitaxial wafer 100 for LEDs, and it isthereby possible to enhance chipping efficiency.

An indicator concerning the warpage after depositing the semiconductorlayer is generally known as BOW. The BOW is inversely proportional tothe thickness of the pattern wafer (1) 10 for LEDs, while beingproportional to the size (diameter) of the pattern wafer (1) 10 for LEDsand the square of the thickness of the semiconductor layer. As the BOWincreases, it is harder to manufacture LED chips, and in considerationof photolithography process in manufacturing LED chips, it is preferablethat the BOW is 1.5 or less. Herein, in consideration of decreasing theBOW, it is preferable to increase the thickness of the pattern wafer (1)10 for LEDs, thin the thickness of the semiconductor layer, and decreasethe size of the pattern wafer (1) 10 for LEDs. However, in the case ofthickening the thickness of the pattern wafer (1) 10 for LEDs, since themanufacturing cost of LED chips is significantly increased and thethermal behavior of the pattern wafer (1) 10 for LEDs changes indepositing the semiconductor layer, deposition properties of thesemiconductor layer may degrade, and the internal quantum efficiency IQEmay decrease. Further, decreasing the size of the pattern wafer (1) 10for LEDs is a factor of significantly degrading the yield of LED chips.In other words, when it is possible to suppress the BOW by thinning thethickness of the semiconductor layer, it is understand that the effectof thinning is significant. Herein, it has been already described thatdeposition properties of the semiconductor layer are enhanced by usingthe uneven structure A. In other words, by using the pattern wafer (1)10 for LEDs provided with the uneven structure A, even when thethickness of the semiconductor layer is thinned, it is possible toeffectively decrease dislocations, and to suppress cracks, and it isthereby possible to reduce the warpage. From this viewpoint, the ratio(Hbun/Have) is preferably 200 or less, and more preferably 150 or less.Further, from the viewpoints of shortening the deposition time of thesemiconductor layer, decreasing a use amount of the semiconductor layer,and achieving environmental supportability, the ratio (Hbun/Have) ismore preferably 100 or less, and most preferably 50 or less. From theforegoing, by the ratio (Hbun/Have) meeting the predetermined range, itis possible to deposit the semiconductor layer high in internal quantumefficiency IQE with cracks suppressed, and to suppress the warpage ofthe pattern wafer (1) 10 for LEDs with the semiconductor layerdeposited, and it is thereby possible to produce high-efficient LEDchips with high efficiency.

<The Ratio (Hbu/Have) of the Distance Hbu to the Average Height (Have)>

The ratio (Hbu/Have) of the distance Hbu to the average height (Have)meets 1.55≦Hbu/Have≦200.

The ratio (Hbu/Have) means the ratio between the average height (Have)of the uneven structure 20 and the average thickness Hbu of the undopedfirst semiconductor layer 31, and as the ratio (Hbu/Have) increases, theaverage thickness Hbu of the undoped first semiconductor layer 31increases. When the ratio (Hbu/Have) is 1.5 or more, the degree offlattening the uneven structure A due to the undoped first semiconductorlayer 31 is enhanced with cracks suppressed. By this means, it ispossible to effectively enhance deposition accuracy of the doped firstsemiconductor layer 32, light emitting semiconductor layer 40 and secondsemiconductor layer 50 provided on the undoped first semiconductor layer31. Therefore, it is possible to reflect crystallinity of the undopedfirst semiconductor layer 31 with few dislocations in the doped firstsemiconductor layer 32, light emitting semiconductor layer 40 and secondsemiconductor layer 50 in a state in which cracks are suppressed, and itis possible to obtain epitaxial wafers for LEDs with cracks suppressedand high internal quantum efficiency IQE while shortening the productiontime. Further, when the ratio (Hbu/Have) is 2.5 or more, flattening ofthe uneven structure 20 is more excellent due to the undoped firstsemiconductor layer 31, in association therewith film thicknessuniformity is enhanced in the light emitting semiconductor layer 40, andin-plane uniformity of emission wavelengths is enhanced. From theviewpoints of more exerting these effects, the ratio is most preferablyis 3.5 or more. Particularly, when the ratio (Hbu/Aave) is 4 or more, itis possible to more decrease the effect of the top of the convex-portionof the uneven structure 20 on the surface of the undoped firstsemiconductor layer 31, and it is thereby possible to achieve moreexcellent flatness of the surface on the light emitting semiconductorlayer 40 of the doped first semiconductor layer 32. In other words, theeffects are increased to enhance the internal quantum efficiency IQE andsuppress cracks. From the same viewpoints, the (Hbu/Aave) is preferably5 or more, more preferably 8 or more, and most preferably 10 or more.Further, from the viewpoints of increasing the probability of collisionbetween dislocations inside the undoped first semiconductor layer 31 andmore increasing the internal quantum efficiency IQE, the ratio(Hbu/Have) is more preferably 12 or more, and most preferably 15 ormore. On the other hand, when the ratio (Hbu/Have) is 200 or less, it ispossible to suppress the warpage of the epitaxial wafer 100 for LEDs.This is capable being determined from the viewpoint of BOW as describedalready. From the same viewpoint, the ratio (Hbu/Have) is preferably 100or less, and more preferably 50 or less. Further, from the viewpoints ofdecreasing a use amount of the semiconductor layer, shortening thedeposition time, and achieving environmental supportability, the ratio(Hbu/Have) is most preferably 30 or less. From the foregoing, by theratio (Hbu/Have) meeting the predetermined range, it is possible todeposit the semiconductor layer high in internal quantum efficiency IQEwith cracks suppressed, and to suppress the warpage of the pattern wafer(1) 10 for LEDs with the semiconductor layer deposited, and it isthereby possible to produce high-efficient LED chips with highefficiency.

<Uneven Structure 20>

As described in <<Pattern wafer (1) for LEDs>>, the uneven structure 20of the epitaxial wafer 100 for LEDs according to this Embodiment i.e.the uneven structure A is not limited particularly, as long as theuneven structure is the uneven structure substantially having regularitywith n-fold symmetry, and the top of the convex-portion is comprised ofthe corner portion with a radius of curvature exceeding “0”. Among thestructures, the crack suppression effect and the effect of improving theinternal quantum efficiency IQE are increased, by meeting therelationship between the Duty and the rotation shift angle Φ describedwith reference to FIG. 8, and the relationship between the averageinterval Pave and the Duty described with reference to FIG. 9. Further,by meeting the relationship between the average interval Pave and theDuty described with reference to FIG. 16, it is possible to concurrentlyincrease the light extraction efficiency LEE. Further preferable aspectsof the uneven structure 20 will be described below.

The uneven structure 20 is capable of adopting the dot-shaped structurecomprised of a plurality of independent convex portions and consecutiveconcave portion, hole-shaped structure comprised of a plurality ofindependent concave portions and consecutive convex portion, or hybridstructure including both a plurality of independent concave portions anda plurality of independent concave portions. Among the structures, thedot-shaped structure is the most preferable. As the reason, thedot-shaped structure makes adherence of the nucleus of the semiconductorlayer and its growth excellent as described already, and increases theeffect of suppressing cracks and the effect of improving the internalquantum efficiency IQE. In the dot-shaped structure, hole-shapedstructure, or hybrid structure, as the contour shape of the bottomportion of one convex portion or the opening shape of one concaveportion, it is possible to adopt the shape of a circle, the shape of anellipse, the shape of a bar, the shape of

, n-gon (n≧3), n-gon (n≧3) having a corner portion with a radius ofcurvature of the corner portion exceeding “0” and the like. Among theshapes, when the portion is in the shape of a circle, the shape of anellipse, the shape of a bar, or triangle having a corner portion with aradius of curvature of the corner portion exceeding “0”, it is possibleto reduce stress applied to the growing semiconductor layer by theuneven structure 20, and therefore, the effect of suppressing cracks isincreased. Particularly, the shape of a circle is the most preferable.In addition, the shape of a circle is substantial circular shape, andslight distortion is considered.

As described already, when the average interval Pave of the unevenstructure 20 meets 50 nm≦Pave≦1500 nm, it is possible to deposit thesemiconductor layer with cracks suppressed and high internal quantumefficiency IQE. Further, in the case of viewing as the epitaxial waferfor LEDs, by the average interval Pave being 1500 nm or less, it ispossible to suitably develop the effect of the ratio (Hbun/Have) orratio (Hbu/Have) as described above. This is because the semiconductorlayer viewed from the uneven structure 20 is increased, and the effectof the ratio (Hbun/Have) or ratio (Hbu/Have) based on the principlesalready described is not disturbed by the uneven structure 20.Accordingly, it is possible to concurrently improve the internal quantumefficiency IQE and cracks. From the same principles, the averageinterval is preferably 1200 nm or less, more preferably 1000 nm or less,and most preferably 950 nm or less. In addition, the lower limit valueis as described already.

<Shape of the Convex Portion>

As the shape of the convex portions constituting the uneven structure20, as described already, from the viewpoints of adherence of thenucleus of the semiconductor layer, growth and coalescence of growingsemiconductor layers, such a structure is preferable that the diameterof the bottom of the convex-portion is larger than the diameter of thetop of the convex-portion, it is more preferable that the side face ofthe convex-portion connecting the top of the convex-portion and thebottom of the concave-portion has tilt angles of two or more stages, andit is the most preferable that the radius of curvature of the point inwhich the tilt changes exceeds “0” to form a curved surface.Particularly, in the case of considering as the epitaxial wafer forLEDs, the aspect ratio that is a parameter representing the shape of theconvex portion i.e. the ratio (Have/(ave) preferably ranges from 0.1 to5.0. First, when the ratio is 0.1 or more, the volume of the convexportion increases from the viewpoint of photons generated from the lightemitting semiconductor layer, and it is thereby possible to increase thelight extraction efficiency LEE. Particularly, in the case where theaspect ratio is 0.3 or more, it is possible to increase the number ofmodes of light diffraction and strengthen scattering properties withrespect to the emitted light, and therefore, such a case is preferable.From the same viewpoints, the aspect ratio is more preferably 0.5 ormore, and most preferably 0.6 or more. On the other hand, when theaspect ratio is 5.0 or less, it is possible to smooth the tilt angle ofthe convex-portion side surface. By this means, it is considered that itis possible to suppress particles occurring in obtaining LED chips. Fromthe viewpoints of the same effects, deposition properties of thesemiconductor layer, and suppression of cracks, the aspect ratio ispreferably 3.0 or less, more preferably 2.0 or less, and most preferably1.1 or less.

<Bottom Portion of the Concave Portion>

As described above, from the viewpoints of adherence of the nucleus ofthe semiconductor layer, growth and coalescence of growing semiconductorlayers, it is preferable that the bottom of the concave-portion has aflat surface. Particularly, in the case of viewing as the epitaxialwafer for LEDs, it is preferable that the flat surface (hereinafter,referred to “flat surface B”) that the bottom of the concave-portion ofthe uneven structure 20 has is parallel to a surface (hereinafter,referred to as “parallel stable growth surface”) almost parallel to astable growth surface of the first semiconductor layer 30. In this case,growth properties of the first semiconductor layer 30 are made excellentin the vicinity of the concave portion of the uneven structure 20, adecrease in dislocations is increased based on coalescence of growingsemiconductor layers, it is thereby possible to effectively dispersedislocations inside the first semiconductor layer 30 corresponding tothe uneven structure 20, and the internal quantum efficiency IQE isthereby enhanced. The stable growth surface refers to a surface with thelowest growth rate in the material to grow. Generally, it is known thatthe stable growth surface appears as a facet surface during the growth.For example, in the case of gallium nitride-based compoundsemiconductor, a plane parallel to the A-axis typified by the M-surfaceis the stable growth surface. The stable growth surface of the GaN-basedsemiconductor layer is the M-surface (1-100), (01-10), (−1010) of ahexagonal crystal, and is one of surfaces parallel to the A-axis. Inaddition, depending on the growth conditions, there is the case wherethe stable growth surface is another plane including the A-axis that isa plane except the M-surface of the GaN-based semiconductor.

<Buffer Layer>

As materials of the buffer layer 33, it is possible to adopt AlGaNstructure, AlN structure, AlInN structure, InGaN/GaN superlatticestructure, InGaN/GaN layered structure, AlInGaN/InGaN/GaN layeredstructure and the like. As deposition of the buffer layer, it ispossible to set the deposition temperature at a range of 350° C. to 600°C. By this means, also for deposition from the narrow bottom of theconcave-portion, it is possible to enhance uniformity. By using thesebuffer layers 33, it is possible to effectively decrease the differencein the lattice constant between the wafer for LEDs and the firstsemiconductor layer 30, and it is possible to improve depositionproperties and crystallinity of the first semiconductor layer 30.Further, the film thickness of the buffer layer 33 is desirably ⅕ orless the average height (Have) of the uneven structure 20. This isbecause of suppressing adherence of the nucleus to the side surfaceportion of the convex portion with respect to re-diffusion andrecrystallization of the buffer layer 33 in the RAMP process. From thisviewpoint, the film thickness of the buffer layer 33 is more preferably1/10 or less, and most preferably 1/20 or less with respect to theaverage height (Have) of the uneven structure 20. Further, it ispreferable that the buffer layer 33 is deposited by MOCVD (Metal OrganicChemical Vapor Deposition) method or sputtering method. Particularly, itis more preferable to adopt the sputtering method, in terms of the factthat uniformity of the buffer layer 33 is enhanced.

<First Semiconductor Layer>

Materials of the first semiconductor layer 30 are capable of beingselected from the undoped first semiconductor layer 31 and doped firstsemiconductor layer 32 as described below. The film thickness (Hbun) ofthe first semiconductor layer 30 is preferably 800 nm or more, from theviewpoints of suppressing cracks to flatten the uneven structure 20,reducing dislocations inside the first semiconductor layer 30,reflecting performance as a semiconductor in the light emittingsemiconductor layer 40 and the second semiconductor layer 50 and therebyincreasing the internal quantum efficiency IQE. Particularly, from theviewpoint of more exerting the effect of reducing dislocations due tothe uneven structure 20, the thickness is preferably 1,500 nm or more,and more preferably 2,000 nm or more. Further, from the viewpoint ofreflecting the performance as a semiconductor in the light emittingsemiconductor layer 40 and the second semiconductor layer 50 andeffectively increasing the internal quantum efficiency IQE, thethickness is preferably 2,500 nm or more, more preferably 3,000 nm ormore, and most preferably 4,000 nm or more. On the other hand, from theviewpoint of the warpage and environmental supportability, the upperlimit value is preferably 100,000 nm or less, more preferably 7,500 nmor less, and most preferably 6,500 nm or less.

The doped first semiconductor layer 32 is not limited particularly, aslong as the layer is capable of being used as an n-type semiconductorlayer suitable for uses of LED. For example, it is possible to applymaterials obtained by doping various elements as appropriate to elementsemiconductors such as silicon and germanium, and chemicalsemiconductors of group III-V, group II-VI, group VI-VI and the like.Particularly, an n-type GaN layer is desirable. As the n-type GaN layer,for example it is possible to supply a silane gas containing NH₃ at3×10⁻² to 4.2×10⁻² mol/min. trimethyl gallium (TMGa) at 0.8×10⁻⁴ to1.8×10⁻⁴ mol/min. and an n-type dopant typified by Si at 5.8×10⁻⁹ to6.9×10⁻⁹ mol/min. to form. From the viewpoint of election injectionproperties to the light emitting semiconductor layer 40, the filmthickness of the doped first semiconductor layer 32 is preferably 800 nmor more, more preferably 1, 500 nm or more, and most preferably 2,000 nmor more. On the other hand, from the viewpoint of reducing the warpage,the upper limit value is preferably 5,000 nm or less. From theviewpoints of reducing a use amount of the doped first semiconductorlayer 32 and shortening the manufacturing time of the epitaxial wafers200, 300 for LEDs, the upper limit value is preferably 4,300 nm or less,more preferably 4,000 nm or less, and most preferably 3,500 nm or less.

The undoped first semiconductor layer 31 is capable of being selected asappropriate within a scope of not interfering with performance as then-type semiconductor layer of the doped first semiconductor layer 32.For example, it is possible to apply element semiconductors such assilicon and germanium, and chemical semiconductors of group III-V, groupII-VI, group VI-VI and the like. Particularly, an undoped nitride layeris preferable. As the undoped nitride layer, for example, it is possibleto supply NH₃ and TMGa onto the buffer layer or wafer for LEDs at a growtemperature of 900° C. to 1500° C. to deposit. From the viewpoint offlattening the uneven structure 20, the film thickness (Hbu) of theundoped first semiconductor layer 31 is preferably 1,000 nm or more.Particularly, from the viewpoint of effectively reducing dislocationsinside the undoped first semiconductor layer 31, the thickness ispreferably 1,500 nm or more, more preferably 2,000 nm or more, and mostpreferably 2,500 nm or more. On the other hand, from the viewpoint ofreducing the warpage of the epitaxial wafer 100 for LEDs, the upperlimit value is preferably 6,000 nm or less. Particularly, from theviewpoint of shortening the manufacturing time of the epitaxial wafers200, 300 for LEDs, the value is preferably 5,000 nm or less, morepreferably 4,000 nm or less, and most preferably 3,500 nm or less.

In addition, when at least the undoped first semiconductor layer 31 anddoped first semiconductor layer 32 are sequentially layered on theuneven structure 20 of the pattern wafer (1) 10 for LEDs, it is alsopossible to further provide another undoped semiconductor layer (2) onthe doped first semiconductor layer 32, and provide the light emittingsemiconductor layer 40 thereon. In this case, as another undopedsemiconductor layer (2), it is possible to use the materials asdescribed in the undoped first semiconductor layer 31 as describedabove. From the viewpoint of light emitting properties of the epitaxialwafers 200, 300 for LEDs, a film thickness of the undoped semiconductorlayer (2) is preferably 10 nm or more, more preferably 100 nm or more,and most preferably 200 nm or more. On the other hand, from theviewpoint of recombination of hole and electron inside the lightemitting semiconductor layer 40, the upper limit value is preferably 500nm or less, more preferably 400 nm or less, and most preferably 350 nmor less.

<Light Emitting Semiconductor Layer>

The light emitting semiconductor layer 40 is not limited particularly,as long as the layer has light emission characteristics as asemiconductor light emitting device (for example, LED). For example, asthe light emitting semiconductor layer 40, it is possible to applysemiconductor layers of AsP, GaP, ALGaAs, InGaN, GaN, AlGaN, ZnSe,AlHaInP, ZnO and the like. Further, the light emitting semiconductorlayer may be doped with various elements as appropriate corresponding tocharacteristics. The light emitting semiconductor layer 40 is an activelayer of single or multiple quantum well structure. For example, at agrowth temperature of 600° C. to 850° C., by using nitrogen as a carrierand gas and supplying NH₃, TMGa and trimethyl indium (TMIn), it ispossible to grow an active layer made of INGaN/GaN in a thickness of 100Å to 1250 Å. Further, in the case of multiple quantum well structure,concerning InGaN forming a single layer, it is also possible to changethe In element concentration. Further, it is possible to provide anelectron block layer between the light emitting semiconductor layer 40and the second semiconductor layer 50. For example, the electron blocklayer is comprised of p-AlGaN.

<Materials of the Second Semiconductor Layer>

Materials of the second semiconductor layer 50 are not limitedparticularly, as long as it is possible to use the materials as thep-type semiconductor layer suitable for uses of LED. For example, it ispossible to apply materials obtained by doping various elements asappropriate to element semiconductors such as silicon and germanium, andchemical semiconductors of group III-V, and group II-VI, group VI-VI andthe like. For example, in the case of the P-type GaN layer, by raisingthe growth temperature to 900° C. or more, and supplying TMGa and CP₂Mg,it is possible to deposit in a thickness of several hundreds tothousands of angstroms (Å).

<Materials of the Pattern Wafer (1) for LEDs>

Materials of the pattern wafer (1) for LEDs are not limitedparticularly, as long as the materials are used as the pattern wafer (1)for LEDs it is possible to use substrates of sapphire, silicon carbide(SiC), silicon nitride (Si₃N₄), gallium nitride (GaN), copper-tungsten(W—Cu), silicon, zinc oxide, magnesium oxide, manganese oxide, zirconiumoxide, manganese oxide-galvanized iron, magnesium aluminum oxide,zirconium boride, gallium oxide, indium oxide, lithium gallium oxide,lithium aluminum oxide, neodymium gallium oxide, lanthanum strontiumaluminum tantalum oxide, strontium titanium oxide, titanium oxide,hafnium, tungsten, molybdenum, GaP, GaAs and the like. Among thesubstrates, from the viewpoint of lattice matching with the firstsemiconductor layer 30, it is preferable to apply sapphire, GaN, GaP,GaAs, silicon carbide, silicon, spinel (for example, insulationsubstrates typified by MgAl₂O₄) and the like. Further, the materials maybe used alone, or a wafer of hetero structure may be used in whichanother wafer is provided on the wafer for LEDs. For example, as thewafer for LEDs, it is possible to use a sapphire wafer with theC-surface (0001) as the main surface. In this case, the M-surface thatis a stable growth surface of the GaN-based semiconductor layer is asurface parallel to the sapphire wafer A-surface (11-20), (1-210),(−2110).

The size of the pattern wafer 1 (10) for LEDs is not limited particular,and examples thereof are 2-inches, 4-inches, 6-inches and 8-inches.These wafers may be the shape of a disk or shape with orientation flat.Herein, from the viewpoints of averaging the effects of the unevenstructure A in terms of deposition phenomenon of the semiconductorlayer, and manufacturing epitaxial wafers for LEDs of high quality, andthe viewpoint of excellently exerting the effect of reducing the warpageof the epitaxial wafer for LEDs among the above-mentioned effects,4-inches or 6-inches is preferable.

Further, the pattern wafer (1) 10 for LEDs may be removed in a stepafter layering at least the first semiconductor layer 30. By removingthe pattern wafer (1) 10 for LEDs, since the effect of disturbing thewaveguide mode is increased, the light extraction efficiency LEE issignificantly enhanced. In this case, the output surface of emittedlight of the LED is preferably the first semiconductor layer 30 sideviewed from the light emitting semiconductor layer 40.

<Transparent Conductive Layer>

The transparent conductive layer 60 is provided on the secondsemiconductor layer 50. For example, the transparent conductive layer 60is formed of a transmission oxide film made of at least one or more ofITO (In₂O₃—SnO₂), ZnO, RuOx, TiOx, IrOx, SnOx, AZnO (ZnO—Al₂O₃), IZnO(In₂O₃—ZnO), GZO (ZnO—Ga₂O₃) and InxOy. Further, it is possible to formthe transparent conductive layer 60 by a vacuum deposition method,sputtering method or CVD (Chemical Vapor Deposition) method.

<Anode Electrode>

The anode electrode 70 is provided on the transparent conductive layer60. As the anode electrode 70, it is possible to use the transmissionoxide film or transparent metal as described in the aforementionedtransparent conductive layer 60. In the case of adopting thetransmission oxide film, it is also possible to cause the interfacebetween the anode electrode 70 and the transparent conductive layer 60to disappear. Further, among the transparent metals are alloys ormulti-layer film containing at least one kind selected from the groupconsisting of Ni, Co, Fe, Ti, Cu, Rh, Au, Ru, W, Zr, Mo, Ta, Pt, oxidesthereof, and nitrides thereof. Particularly, in terms of adhesion force,preferable is a multi-layer film with Au layered on Ni. Further, forexample, it is possible to adopt a multi-layer film with Au layered onNi and RhO layered on the Au.

<Cathode Electrode>

The cathode electrode 80 is formed on an exposed surface of the firstsemiconductor layer 30 obtained by etching the first semiconductor layer30 from the second semiconductor layer 50 side. For example, it ispossible to use metals such as gold, silver, titanium and chromium andmetal oxides. Particularly, a metal multi-layer film is preferable.

<Reflecting Film>

It is possible to form a reflecting film on the surface opposite to theuneven structure 20 of the pattern wafer (1) 10 for LEDs. By forming thereflecting film, it is possible to more increase the light extractionefficiency LEE due to the uneven structure 20. The reflectance of thereflecting film is preferably 80% or more, more preferably 90% or moreand most preferably 91% or more at a light emission wavelength of thelight emitting semiconductor layer 40. For example, it is possible touse a dielectric multi-layer film. The dielectric multi-layer film is amulti-layer film obtained by alternately layering two or more dielectricmaterials with different refractive indexes. For example, it is possibleto layer ZrO₂, AlN, Nb₂O₃ or Ta₂O₃ and SiO₂ with the number of pairs of3 to 8.

<Manufacturing Method of the Uneven Structure 20>

Described above are the epitaxial wafer 100 for LEDs and pattern wafer(1) 10 for LEDs according to this Embodiment. Manufacturing methods ofthe uneven structure 20 will be described next.

It is possible to manufacture by a transfer method, photolithographymethod, thermal lithography method, electron beam lithography method,interference exposure method, lithography method using nanoparticles asa mask, lithography method using a self-organizing structure as a maskand the like. Particularly, from the viewpoints of processing accuracyand processing speed of the uneven structure 20 of the pattern wafer (1)10 for LEDs, it is preferable to adopt the transfer method.

The transfer method in the present description is defined as a methodincluding a step of transferring a fine pattern of a mold provided withthe fine pattern on its surface to a wafer for LEDs (pattern wafer (1)10 for LEDs without the uneven structure 20 being prepared yet). Inother words, the method is a method including at least a step of bondingthe fine pattern of the mold to the wafer for LEDs via a transfermaterial, and a step of peeling off the mold. By adopting this method,it is possible to meet the rotation shift angle Θ as described abovewith ease. More specifically, it is possible to classify the transfermethod into two. First, there is the case of using a transfer materialthat is transfer-added to the wafer for LEDs as a permanent material. Inthis case, the wafer for LEDs is different from materials constitutingthe uneven structure 20. Further, it is a feature that the unevenstructure 20 remains as the permanent material and is used as theepitaxial wafer 100 for LEDs. In this case, in order to ensure growthproperties of the first semiconductor layer 30, it is preferable toadopt a method of partially exposing the surface of the wafer for LEDs.In other words, the method makes a state in which the transfer materialis partially disposed on the surface of the wafer for LEDs, and thepartially disposed transfer material functions as a mask for inhibitinggrowth of the first semiconductor layer 30. Since the LED is used over along term such as several tens of thousands of hours, in the case ofusing the transfer material as the permanent material, it is preferablethat materials constituting the transfer material contain the metalelement. Particularly, by containing metal alkoxide causing hydrolysisand polycondensation reaction, or condensation compound of metalalkoxide in raw materials, performance as the permanent material isincreased, and therefore, such materials are preferable. A morepreferable method is to transfer and add a mask material typified bySiO₂ deposited by a vacuum process such as deposition and sputtering.Further, a mask is partially formed on the wafer for LEDs by thetransfer method, and next, an inorganic material typified by SiO₂ isdeposited by deposition or sputtering. Subsequently, by removing themask prepared by the transfer method, it is also possible to pattern theinorganic material on the wafer for LEDs. Alternatively, it is possibleto beforehand deposit a layer of an inorganic material on the mainsurface of the wafer for LEDs, and process the layer of the inorganicmaterial by the transfer method to obtain. When materials of the waferfor LEDs and the uneven structure 20 are different as described above,as the uneven structure 20, it is the most preferable to adopt one or amixture of two or more of metal aluminium, amorphous aluminium oxide,polycrystalline aluminium oxide, polycrystalline sapphire, silicon oxide(SiO₂), silicon nitride (Si₃N₄), silver (Ag), chromium (Cr), nickel(Ni), gold (Au) and platinum (Pt). By this means, it is possible toexert the effects of the rotation shift angle Θ completely.

Second, there is a nanoimprint lithography method. The nanoimprintlithography method is a method including a step of transferring a finepattern of a mold onto the wafer for LEDs, a step of providing a mask toprocess the wafer for LEDs by etching, and a step of etching the waferfor LEDs. For example, in the case of using one kind of transfermaterial, first, the wafer for LEDs and mold are bonded via the transfermaterial. Next, the transfer material is cured by heat or light (UV),and the mold is peeled off. Etching typified by oxygen ashing isperformed on the uneven structure comprised of the transfer material topartially expose the wafer for LEDs. Subsequently, the wafer for LEDS isprocessed by etching using the transfer material as a mask. As theprocessing method at this point, it is possible to adopt dry etching andwet etching. In the case of intending to increase the height h of theuneven structure 20 of the pattern wafer (1) 10 for LEDs, dry etching isuseful. Further, for example, in the case of using two kinds of transfermaterials, a first transfer material layer is first formed on the waferfor LEDs. Next, the first transfer material layer and mold are bondedvia a second transfer material. Subsequently, the transfer material iscured by heat or light (UV) to peel off the mold. Etching typified byoxygen ashing is performed on the uneven structure comprised of thesecond transfer material to partially expose the first transfermaterial. Next, using the second transfer material layer as a mask, thefirst transfer material layer is etched by dry etching. Subsequently,using the transfer material as a mask, the wafer for LEDs is processedby etching. As the processing method at this point, it is possible toadopt dry etching and wet etching. In the case of intending to increasethe height h of the uneven structure 20, dry etching is useful.

Further, as the nanoimprint lithography method, it is also possible toadopt a nano-fabrication sheet method that eliminates the need forresidual film processing as described below. A diluted mask layer (2)material is applied onto the uneven structure surface of the mold, andthe solvent is removed. By this operation, the mask layer (2) is capablebeing disposed inside the concave portion of the mold. A diluted masklayer (1) material is applied on the uneven structure of the mold withthe mask layer (2) included inside the concave portion of the mold, andthe solvent is removed. By this operation, the mask layer (2) is filledinto the inside of the concave portion of the mold, and it is possibleto deposit the mask layer (1) to fill and flatten the uneven structureand mask layer (2). By this means, a nano-fabrication sheet ismanufactured. Then, the mask layer (1) of the nano-fabrication sheet islayered to the wafer for LEDs for lamination. Then, an energy linetypified by UV light is applied to peel off the mold. Dry etching isperformed on obtained mask layer (2)/mask layer (1)/wafer for LEDs fromthe mask layer (2) surface side to expose partially the wafer for LEDs.Next, by etching over the mask layer, it is possible to process thewafer for LEDs and manufacture the pattern wafer (1) 10 for LEDs.Particularly, by adopting the nano-fabrication sheet method, it ispossible to control the arrangement direction of the uneven structureusing the direction in which the sheet is bonded. For example, thenano-fabrication sheet is fed out and set in a winding apparatus. Next,the wafer for LEDs is loaded. A position of orientation flat of thewafer for LEDS at this point is detected and controlled. Then, thenano-fabrication sheet is bonded to the loaded wafer for LEDs. In otherwords, although the nano-fabrication sheet is bonded in a particulardirection mechanically, by controlling the direction of the wafer forLEDs that is a target for bonding, it is possible to easily control therotation shift angle Θ. Resolution of the rotation shift angle Θ was±1°.

As described above, by adopting the transfer method, since it ispossible to reflect the fine pattern of the mold in the wafer for LEDs,it is possible to obtain excellent pattern wafers (1) 10 for LEDs.

By applying the transfer method typified by the nanoimprint lithographymethod and the nano-fabrication sheet method, it is possible to transferand form the mask layer to process and form the uneven structure 20 onthe main surface of the wafer for LEDs. Herein, the dry etching methodis described in manufacturing the uneven structure 20 using the masklayer. Particularly, the method is effective in the case where two ormore mask layers are provided on the wafer for LEDs. For example, in thecase of laminating in the order of organic resist/inorganic resist fromthe main surface side of the wafer for LEDs, and using the mask layerhaving the uneven structure comprised of the organic resist andinorganic resist, the effect of the dry etching method as describedbelow is developed at the maximum.

In the following description, an etching processed material refers to alaminate in which a mask layer used to form the uneven structure 20 byperforming dry etching processing on the wafer for LEDs is disposed onthe main surface of the wafer for LEDs. The etching processed materialis an etching processed material provided with a mask layer having apattern with a pattern width of 5 μm or less and an aspect ratio of 0.1to 5.0 on the wafer for LEDs, and an entire thermal resistance value ispreferably 6.79×10⁻³ (m²·K/W) or less in placing the etching processedmaterial on a placement member used in etching processing. The thermalresistance value is a value obtained by dividing a thickness of a memberby thermal conductivity λ of materials forming the member.

By this configuration, etching damage is reduced to the mask layer byheat generated in etching processing, and it is possible to manufacturethe pattern wafer (1) for LEDs having the desired uneven structure 20 byetching. Further, by using the placement member that is a component ofthe etching processed material as a transport member, it is possible toincrease throughput in the dry etching process.

The etching processed material is placed on a placement region of theplacement member. Further, the etching processed material may bedirectly placed on the placement region of the placement member or maybe placed via another member such as a heat transfer sheet. In eithercase, it is important that the entire thermal resistance value is6.79×10⁻³ (m²·K/W) or less. Herein, using the case where the etchingprocessed material is disposed on the placement region of the placementmember via a heat transfer sheet as an example, the entire thermalresistance value is the sum of a thermal resistance value of theplacement member in the placement region, a thermal resistance value ofthe etching processing member, and a thermal resistance value of theheat transfer sheet. In addition, it is possible to replace the heattransfer value with another member to read. Further, in the case of notusing another member typified by the heat transfer sheet, the thermalresistance value of the heat transfer sheet is made “0”.

The thermal resistance value is a value obtained by dividing a thicknessof a member by thermal conductivity λ of materials forming the member.In other words, the thermal resistance value R (m²·K/W) is a valuecalculated by thickness d (m) of the member/thermal conductivity λ(W/m·K) of the member. Materials and thicknesses of members and layersforming the etching processed material and materials and thicknessesforming the placement member are adjusted so that the entire thermalresistance value is R≦6.79×10⁻³ (m²·K/W). In other words, by applyingconditions meeting the range of the entire thermal resistance value Rand performing dry etching, it is possible to manufacture the patternwafer (1) for LEDs with high accuracy. As the entire thermal resistancevalue, it is more preferable that the value is R≦3.04×10⁻³ (m²·K/W) orless, and it is further preferable that the value is R≦1.21×10⁻³(m²·K/W) or less. In addition, as the lower limit value of the entirethermal resistance value R, it is preferable that 0≦R. In addition, itis possible to measure the thermal resistance value with ease by a laserflash method.

Concerning the thickness d of the placement member, there is no lowerlimit from the viewpoint of the thermal resistance value, however, whenthe thickness d of the placement member is too small, since there is apossibility of breakage at the time of transporting the placement memberand the like, it is preferable to adopt a range for providing durabilitye.g. 0.001 m or more. Further, there is an upper limit value of theconsiderable thickness d from the viewpoint of the thermal resistancevalue, and at the same, from the viewpoints of operability in transportand the cost, the thickness d of the placement member is preferably 0.05m or less.

The placement member is a member to place the etching processedmaterial, and is capable of being used as a transport tray to fix ortransport the etching processed material. By using the placement member,it is possible to reduce misalignment of the etching processed materialin transporting the etching processed material to a vacuum reactor of adry etching apparatus, and to concurrently transport a plurality ofetching processed materials, and the throughput is thereby increased. Asmaterials forming the placement member, examples thereof are metalmaterials such as silicon (Si), aluminium (Al) and stainless, ceramicssuch as quartz (SiO₂), silicon carbide (SiC), silicon nitride (SiN),alumina (Al₂O₃), aluminium nitride (AlN), zirconium oxide (ZrO₂) andyttrium oxide (Y₂O₃), and metal materials such as silicon and aluminiumcoated with alumite, yettirum and aluminium with ceramic thermallysprayed onto the surface, and silicon and aluminium coated with resinmaterial. These materials are not limited particularly, as long as thematerials meet the above-mentioned condition of the entire thermalresistance value R, and it is preferable to select materials that do notgenerate a reactant with high deposition property against a dry etchinggas. As more preferable examples, silicon (Si), quartz (SiO₂) andaluminium (Al) are preferable in terms of availability and highprocessability of the placement member, and silicon carbide (SiC),alumina (Al₂O₃), aluminium nitride (AlN), zirconium oxide (ZrO₂),yttrium oxide (Y₂O₃) and inorganic members coated with one or morethereof are particularly preferable in terms of the respect that thereactant with high deposition properties is hard to occur. In addition,specifically, the inorganic members used herein are metal materials suchas silicon (Si) and aluminium with high processability, for example. Bycoating such an inorganic member with a material such as silicon carbide(SiC) that does not generate the reactant with high depositionproperties, it is possible to achieve compatibility between processingeasiness and support for dry etching. Further, in this case, inaluminium nitride (AlN) and the like, there is a case where 100% thereofdoes not become aluminium nitride (AlN), a part thereof becomes alumina(Al₂O₃) and the like, and the coating layer is a mixture. Accordingly,the description of “coated with one or more thereof” means that the casewhere another material coexists in coating with some material isincluded.

Shapes of the placement member are not limited particularly when thecondition of the above-mentioned entire resistance value R is satisfied,and examples thereof are the shape of a thin-sheet circle and the shapeof a thin-sheet rectangle. The surface of the placement member does notneed to be flat, and a concave portion (counter bore, pocket) may beformed to store the etching processed material. Further, the placementmember does not need to be comprised of a single material, and may becomprised of two or more kinds of materials. Furthermore, the placementmember does not need to be formed of a single structure, and may becomprised by combining two or more kinds of structures such as a baseportion and portion like a lid to cover a part of the etching processedmaterial and thereby fix the etching processed material.

By the dry etching processing that meets the range of the thermalresistance value R as described above, it is possible to reduce etchingdamage. By this means, it is possible to manufacture the pattern wafer(1) for LEDs having the uneven structure A with high accuracy. Herein,as the mask layer, two or more mask layers are preferable as describedalready, and are capable of being prepared with ease by thenano-fabrication sheet method or nanoimprint method on two or moreresist layers. Particularly, by using the nano-fabrication sheet, it ispossible to form two or more mask layers with high accuracy.

For example, by applying the transfer method, two resist layers areobtained on the main surface of the wafer for LEDs. For example, it isassumed that deposition is performed in the order of organicresist/inorganic resist from the side closer to the wafer for LEDs, andthat at least the inorganic resist forms the uneven structure. In thiscase, first, in the case of the nanoimprint method, it is necessary topartially remove a residual film existing on the inorganic resist andorganic resist, and in the case of the nano-fabrication sheet, only theorganic layer is partially removed. This step is called the residualfilm removal step. In the residual film removal step, for example, it ispreferable to use reactive etching with a gas containing at least onekind of O₂ gas, H₂ gas, Xe gas and Ar gas. For example, when the etchingpressure ranges from 0.1 Pa to 5 Pa, the processing accuracy isenhanced. Particularly, by using only the O₂ gas, or a gas by adding theAr gas to the O₂ gas in an amount of 50 volume % or less, the processingaccuracy is enhanced. By this means, it is possible to form a finepattern mask with a high aspect ratio on the wafer for LEDs.

In the fine pattern mask formation step, it is always not necessary touse the placement member, and it is not necessary to select the materialand shape of each member so as to meet the range of the entire thermalresistance value R as described previously either.

In an etching method to enhance the processing accuracy of the unevenstructure 20 of the pattern wafer (1) for LEDs, the etching processedmaterial is obtained which is provided with a mask layer having apattern width of 5 μm or less and an aspect ratio of 0.1 to 5.0 on thewafer for LEDs, and is placed on the placement member, and the wafer forLEDs is etched using the mask layer as a mask in a state in which theentire thermal resistance value R is 6.79×10⁻³ (m²·K/W) or less. By thismeans, since etching damage is suppressed to the fine pattern mask,etching uniformity of the fine pattern mask is kept in the etching step,and the accuracy of the uneven structure 20 is enhanced in the patternwafer (1) for LEDs.

From the viewpoint of etching the wafer for LEDs, it is possible toperform etching using a chlorine-based gas and fluorocarbon-based gas.Among fluorocarbon-based gases (CxHzFy: x=1 to 4, y=1 to 8, and z=0 to 3of integers in these ranges) easy to perform reactive etching on thewafer for LEDS, a mixed gas containing at least one kind is used. As thefluorocarbon-based gases, examples thereof are CF₄, CHF₃, C₂F₆, C₃F₈,C₄F₆, C₄F₈, CH₂F₂, and CH₃F. Further, in order to enhance the etchingrate of the wafer for LEDs, used is a mixed gas obtained by mixing Argas, O₂ gas, and Xe gas to the fluorocarbon-based gas in an amount of50% or less of the entire gas flow rate. In the case of etching thewafer for LEDs (hard etching substrate) hard to undergo the reactiveetching with the fluorocarbon-based gas and the case of etching thewafer for LEDs that generates a reactant with high depositionproperties, a mixed gas is used which contains at least one amongchlorine-based gases capable of performing reactive etching. As thechlorine-based gases, examples thereof are Cl₂, BCl₃, CCl₄, PCl₃, SiCl₄,HCl, CCl₂F₂ and CCl₃F. Further, in order to enhance the etching rate ofthe hard etching substrate, the O₂ gas, Ar gas or mixed gas of O₂ gasand Ar gas may be added to the chlorine-based gas.

Since ion incident energy contributing to the reactive etching isincreased and the etching rate of the wafer for LEDs is enhanced, thepressure in the etching preferably ranges from 0.1 Pa to 20 Pa, and morepreferably ranges from 0.1 Pa to 10 Pa.

Further, by mixing two kinds of fluorocarbon gases with different ratios(y/x) of C and F (CxHzFy: x=1 to 4, y=1 to 8, and z=0 to 3 of integersin these ranges) to increase or decrease the deposition amount of thefluorocarbon film to protect etching side walls of the wafer for LEDs,it is possible to independently create the angle of the taper shape ofthe fine pattern prepared for the wafer for LEDs. In the case ofcontrolling the shape of the mask for the wafer for LEDs with higheraccuracy by dry etching, the ratio between the flow rate of fluorocarbongas with F/C≧3 and the flow rate of fluorocarbon gas with F/C<3 ispreferably 95 sccm:5 sccm to 60 sccm:4.0 sccm, and more preferably 70sccm:30 sccm to 60 sccm:40 sccm. Also in the case where the total flowrate of gas is changed, the above-mentioned flow rate ratios are notchanged.

Furthermore, as the mixed gas of fluorocarbon-based gas and Ar gas andmixed gas of O₂ gas or Xe gas, when the reactive etching component andion incident component are proper amounts, from the viewpoint ofenhancing the etching rate of the wafer for LEDs, the ratio of gas flowrates is preferably 99 sccm:1 sccm to 50 sccm:50 sccm, more preferably95 sccm:5 sccm to 60 sccm:40 sccm, and further preferably 90 sccm:10sccm to 70 sccm:30 sccm. Further, as the mixed gas of chlorine-based gasand Ar gas and mixed gas of O₂ gas or Xe gas, when the reactive etchingcomponent and ion incident component are proper amounts, from theviewpoint of enhancing the etching rate of the wafer for LEDs, the ratioof gas flow rates is preferably 99 sccm:1 sccm to 50 sccm:50 sccm, morepreferably 95 sccm:5 sccm to 80 sccm:20 sccm, and further preferably 90sccm:10 sccm to 70 sccm:30 sccm. Also in the case where the total flowrate of gas is changed, the above-mentioned flow rate ratios are notchanged.

Still furthermore, for etching of the wafer for LEDs using thechlorine-based gas, it is preferable to use only BCl₃ gas, or a mixedgas of a mixed gas of BCl₃ gas and Cl₂ gas and the Ar gas or Xe gas. Inthese mixed gases, when the reactive etching component and ion incidentcomponent are proper amounts, from the viewpoint of enhancing theetching rate of the wafer for LEDs, the ratio of gas flow rates ispreferably 99 sccm:1 sccm to 50 sccm:50 sccm, more preferably 99 sccm:1sccm to 70 sccm:30 sccm, and most preferably 99 sccm:1 sccm to 90sccm:10 sccm. Also in the case where the total flow rate of gas ischanged, the above-mentioned flow rate ratios are not changed.

As plasma etching, it is possible to use capacity coupling type RIE,inductive coupling type RIE, inductive coupling type RIE or RIE usingion drawing-in voltage. For example, using only the CHF₃ gas or a gasobtained by mixing CF₄ and C₄F₈ in the ratio of gas flow rates of 90sccm:10 sccm to 60 sccm:40 sccm, the processing pressure is set in therange of 0.1 Pa to 5 Pa, and used is capacity coupling type RIE, or RIEusing ion drawing-in voltage. Further, for example, in the case of usingthe chlorine-based gas, used is only the BCl₃ gas, or a gas obtained bymixing the BCl₃ gas and Cl₂ gas or Ar gas in the gas flow rate ratio of95 sccm:5 sccm to 85 sccm:15 sccm, the processing pressure is set in therange of 0.1 Pa to 10 Pa, and used is capacity coupling type RIE,conductive coupling type RIE or RIE using ion drawing-in voltage.

Moreover, for example, in the case of using the chlorine-based gas, usedis only the BCl₃ gas, or a gas obtained by mixing the BCl₃ gas and Cl₂gas or Ar gas in the gas flow rate ratio of 95 sccm:5 sccm to 70 sccm:30sccm, the processing pressure is set in the range of 0.1 Pa to 10 Pa,and used is capacity coupling type RIE, conductive coupling type RIE orRIE using ion drawing-in voltage. Further, also in the case where thetotal gas flow rate of the mixed gas used in etching is changed, theabove-mentioned flow rate ratio is not changed.

In the dry etching step for the wafer for LEDs, etching is performed onthe wafer for LEDs in the state of the etching processed material in therange of the entire thermal resistance value R as described previously.By thus performing dry etching on the wafer for LEDs, also in the caseof using, as a mask, the fine pattern mask with the pattern width of 5μm or less and the aspect ratio in the range of 0.1 to 5.0, whileensuring high throughput, it is possible to reduce dry etching damageand form the uneven structure for the wafer for LEDs as expected.

The fine pattern mask formation step and the dry etching step for thewafer for LEDs may undergo successive processing in the same apparatus.In this case, the placement member is also used in the fine pattern maskformation step, and each material and shape are selected so as to meetthe range of the entire thermal resistance value R as describedpreviously.

<<Manufacturing Method of the Epitaxial Wafer for LEDs>>

Described next is a method of manufacturing the epitaxial wafer 100 forLEDs. It is possible to manufacture the epitaxial wafer 100 for LEDsaccording to this Embodiment by sequentially depositing the firstsemiconductor layer 30, light emitting semiconductor layer 40, andsecond semiconductor layer 50 on the uneven structure 20 of the patternwafer (1) 10 for LEDs so as to meet the ratio (Hbun/Have) and/or theratio (Hbu/Have) as described above. Particularly, it is preferable toinclude the step of preparing the pattern wafer (1) 10 for LEDs, thestep of performing optical measurement on the pattern wafer (1) 10 forLEDs, and the step of manufacturing the epitaxial wafer 100 for LEDsusing the pattern wafer (1) 10 for LEDs in this order. In this case,since it is possible to beforehand evaluate accuracy of the patternwafer (1) 10 for LEDs, it is possible to estimate the degree ofimprovements in internal quantum efficiency IQE and light extractionefficiency LEE in advance. As the optical measurement, it is possible toadopt both measurement for detecting reflected light and measurement fordetecting transmitted light. Particularly, since it is possible todivert apparatuses with high general versatility, in the case ofdetecting transmitted light, it is preferable to measure the haze. Onthe other hand, from the viewpoint of judging the accuracy of the unevenstructure 20 more accurately, the scheme for detecting reflected lightis preferable. In this case, according to the arrangement and size ofthe uneven structure 20, it is possible to set whether to detect aregular reflection component or a diffuse reflection component asappropriate. By using the regular reflection component, it is possibleto evaluate accuracy of the contour shape of the uneven structure 20,and by using the diffuse reflection component, it is possible toevaluate volume accuracy of the uneven structure 20. It is possible toselect which component to adopt as appropriate according to the useduneven structure 20 and the purpose. Further, it is also possible to usea ratio between the diffuse reflection component and the regularreflection component, (diffuse reflection component-regular reflectioncomponent), (diffuse reflection component-regular reflectioncomponent)/regular reflection component, (diffuse reflectioncomponent-regular reflection component)/diffuse reflection component andthe like. In the above-mentioned optical measurement, by making thewavelength of the light source larger than the average interval (Pave)of the uneven structure 20, it is also possible to effectively evaluatethe defect of the uneven structure 20.

As described above, by using the pattern wafer (1) for LEDs, developedare the effects of the rotation shift angle Θ and the shape of the topof the convex-portion, and it is thereby possible to suppress cracks inthe semiconductor layer excellently. Then, it is possible to effectivelyimprove the internal quantum efficiency IQE. Herein, by using a patternwafer (2) for LEDs as described below, it is possible to more improvethe light extraction efficiency LEE, while maintaining the effects asdescribed above. The pattern wafer (2) for LEDs is characterized byfurther providing another uneven structure L to the pattern wafer (1)for LEDs. By the uneven structure L, it is possible to provide stronglight scattering properties and more enhance the light extractionefficiency LEE.

Concerning the pattern wafer (2) for LEDs, the uneven structure Acorresponds to the uneven structure A described in the pattern wafer (1)for LEDs. In other words, the pattern wafer (2) for LEDs is obtained byadding the uneven structure L to the pattern wafer (1) for LEDs as afurther uneven structure. Therefore, in addition to the effects due tothe pattern wafer (1) for LEDs, it is possible to develop effects due tothe newly added uneven structure L. Accordingly, in addition toeffectively suppressing cracks, significantly enhancing crystallinity ofthe semiconductor layer, and enhancing the internal quantum efficiencyIQE, it is made possible to effectively enhance the light extractionefficiency LEE.

The pattern wafer (2) for LEDs will specifically be described below. Inaddition, as described already, the pattern wafer (2) for LEDs isobtained by further adding the uneven structure L to the pattern wafer(1) for LEDs. Accordingly, in the following description, the descriptionof the added uneven structure L will be given mainly. Therefore,detailed descriptions are omitted on the other components of the patternwafer (2) for LEDs, epitaxial wafer for LEDs using the pattern wafer (2)for LEDs, LED chip using the pattern wafer (2) for LEDs, andmanufacturing method of the pattern wafer (2) for LEDs, and for thesematters, it is possible to apply the matters of the pattern wafer (1)for LEDs without modification.

Further, the definitions described in the description of the patternwafer (1) for LEDs are also applied to the pattern wafer (2) for LEDs.

The pattern wafer (2) for LEDs according to this Embodiment ischaracterized by being provided with the uneven structure A having anarrangement with n-fold symmetry substantially and the uneven structureL having an arrangement with m-fold symmetry substantially that isdifferent from the uneven structure A on the main surface, where in atleast a part of the uneven structure A, the rotation shift angle Θ meets0°<Θ≦(180/n)° in which Θ is the rotation shift angle of the arrangementaxis A of the uneven structure A with respect to a crystal axisdirection of the pattern wafer (2) for LEDs in the main surface. Inother words, the pattern wafer (2) for LEDs according to this Embodimentis characterized by being further provided with the uneven structure Lhaving the arrangement with m-fold symmetry substantially, differentform the uneven structure A, on the surface with the concavo-convex Aexisting of the pattern wafer (1) for LEDs.

According to this configuration, it is possible to increase the internalquantum efficiency IQE of the epitaxial wafer for LEDs using the patternwafer (2) for LEDs, and to suppress cracks inside the semiconductorlayer deposited on the surface (hereafter, uneven structure) having theuneven structure of the pattern wafer (2) for LEDs. Further, it ispossible to extract the light efficiently emitted from the LED to theoutside of the LED. In other words, it is possible to develop theeffects as described in the pattern wafer (1) for LEDs, and to furtherachieve increases in light extraction efficiency LEE due to the unevenstructure L.

First, since the uneven structure A of the pattern wafer for LEDs is theuneven structure A of the pattern wafer (1) for LEDs as describedalready, from the same principles, it is possible to deposit thesemiconductor layer with cracks reduced, and it is thereby possible toobtain the semiconductor crystal of high quality. Further, it ispossible to improve the internal quantum efficiency IQE of the epitaxialwafer for LEDs. Hereinafter, the effects of the uneven structure A aredescribed, and are capable of being replaced with the same effects asthe effects due to the uneven structure 20 of the pattern wafer (1) forLEDs to read.

In the pattern wafer (2) for LEDs according to this Embodiment, theuneven structure L is comprised of pluralities of convex portions andconcave portions having a first average interval (PL), and the unevenstructure A is provided on surfaces of at least either the convexportions or the concave portions forming the uneven structure L, and iscomprised of pluralities of convex portions and concave portions havinga second average interval (PA), where it is preferable that the ratio(PL/PA) of the first average interval (PL) to the second averageinterval (PA) exceeds 1 and is 2000 or less. Herein, the second averageinterval (PA) refers to the average interval (Pave) described in thepattern wafer (1) for LEDs.

According to this configuration, it is possible to prevent the effectsof the uneven structure A from being suppressed by the uneven structureL, and to increase a difference between the uneven structure A and theuneven structure L as viewed from the emitted light. That is, it ispossible to effectively develop the function of the pattern wafer (1)for LEDs, and further increase the light extraction efficiency LEE. Thelight extraction efficiency LEE is due to provision of large opticalscattering properties due to the uneven structure L.

In the pattern wafer (2) for LEDs according to this Embodiment, it ispreferable that a plurality of the convex portions forming the unevenstructure L is mutually spaced, and that the convex portions or concaveportions forming the uneven structure A are provided at least in bottomportions of a plurality of the concave portions forming the unevenstructure L.

According to this configuration, development of the effects of theuneven structure A is particularly made excellent. By the unevenstructure A provided on the concave portions of the uneven structure L,it is possible to grow the semiconductor layer preferentially from thebottom portion of the concave portion of the uneven structure L. Herein,since the uneven structure A is provided on the bottom portion of theconcave portion, from the principles described already, it is possibleto effectively achieve suppression of cracks and improvements ininternal quantum efficiency IQE.

In the pattern wafer (2) for LEDs according to this Embodiment, it ispreferable that a plurality of the concave portions forming the unevenstructure L is mutually spaced, and that the convex portions or concaveportions forming the uneven structure A are provided at least on tops ofa plurality of the convex portions forming the uneven structure L.

According to this configuration, particularly, it is possible toincrease the light extraction efficiency LEE. By the uneven structure Aprovided on the vertex portion of the convex portion of the unevenstructure L with a larger average interval, it is possible to developthe effect of crack suppression and the effect of improvements ininternal quantum efficiency IQE in the semiconductor layer growing fromthe top of the convex-portion of the uneven structure L. In this case,it is possible to form space in which the semiconductor layer is notdeposited in the concave portion of the uneven structure L. This spaceis extremely low in the refractive index from the viewpoint of thesemiconductor layer. In other words, since it is possible to increasethe difference in the refractive index, optical scattering propertiesare increased, and the light extraction efficiency LEE is more enhanced.Further, it is made easy to remove the pattern wafer (2) for LEDs, andtherefore, depending on the type of LED, it is possible to cause laserliftoff to suitably act.

In the pattern wafer (2) for LEDs according to this Embodiment, it ispreferable that a coverage of the uneven structure A to the unevenstructure L exceeds 0% and is less than 100%.

According to this configuration, by the coverage exceeding 0%, it ispossible to exert the effects due to the uneven structure A as describedabove i.e. the effects of suppressing cracks and improving the internalquantum efficiency IQE. On the other hand, by the coverage being lessthan 100%, it is possible to keep excellent adherence of the nucleus ofthe semiconductor layer and growth properties. Therefore, the growthproperties of the semiconductor layer are made excellent, cracks aresuppressed, and it is possible to deposit the semiconductor layer withhigh internal quantum efficiency IQE.

In the pattern wafer (2) for LEDs according to this Embodiment, theuneven structure A is comprised of pluralities of convex portions andconcave portions having a first average interval (PA), and the unevenstructure L is provided on the surface of the uneven structure A apartfrom each other so as to expose a part of the uneven structure A, and iscomprised of a plurality of convex portions having a second averageinterval (PL), where it is preferable that the ratio (PL/PA) between thefirst average interval (PA) and the second average interval (PL) exceeds1 and is 2000 or less. Herein, the first average interval (PA) refers tothe average interval (Pave) described in the pattern wafer (1) for LEDs.

According to this configuration, it is possible to develop the effectsof the uneven structure A and to increase the light extractionefficiency LEE. First, since the pattern wafer (2) for LEDs has theuneven structure A on its surface and the uneven structure A includesthe exposed portion, from the principles described already, cracks aresuppressed, and it is possible to deposit the semiconductor layer withhigh internal quantum efficiency IQE. Next, the uneven structure L isprovided on the surface of the uneven structure A. The uneven structureL has a larger average interval than that of the uneven structure A.Accordingly, optical scattering properties are strengthened. In otherwords, it is possible to deposit the semiconductor layer with crackssuppressed, and since dislocations of the semiconductor layer aredecreased, the internal quantum efficiency IQE is increased. Then, it ispossible to extract the light effectively emitted by high internalquantum efficiency IQE to the outside of the LED by optical scatteringproperties.

In the pattern wafer (2) for LEDs according to this Embodiment, theaverage interval (PA) of the uneven structure A preferably ranges from50 nm to 1500 nm. Herein, the average interval (PA) refers to theaverage interval (Pave) described in the pattern wafer (1) for LEDs.

According to this configuration, from the principles described in thepattern wafer (1) for LEDs, the effects due to the uneven structure Aare more enhanced.

In the pattern wafer (2) for LEDs according to this Embodiment, in usingthe Duty (Φave/PA) that is a ratio of the average diameter (Φave) of thebottom of the convex-portion of the uneven structure A to the averageinterval (PA), it is preferable that the rotation shift angle Θ meets arange of a tan(Duty/2)°≦Θ≦(180/n)°.

According to this configuration, from the same principles as in thepattern wafer (1) for LEDs, the effects of the uneven structure A aremore remarkable. Accordingly, the internal quantum efficiency IQE ismore increased, and cracks occurring in the semiconductor layer areeffectively suppressed.

In the following description, the expression of uneven structure AL isused, in the case of describing the uneven structure A and the unevenstructure L at the same time. The pattern wafer (2) for LEDs accordingto this Embodiment is provided on its surface with the uneven structureAL. The uneven structure AL may be obtained by processing one mainsurface of the wafer for LEDs or may be provided on one main surface ofthe wafer for LEDs separately. In other words, materials constitutingthe wafer for LEDs may be the same as or different from materialsconstituting the uneven structure A and/or uneven structure L. Herein,the uneven structure A substantially has an arrangement with n-foldsymmetry, the rotation shift angle Θ described already exhibits apredetermined range, and the shape of the top of the convex-portion is acorner portion with a radius of curvature exceeding “0”. In addition, asdescribed already in the pattern wafer (1) for LEDs, the shape of thetop of the convex-portion is also capable of including a tabletop of thesize of 100 nm or less.

The relationship between the arrangement of the uneven structure A andthe arrangement of the uneven structure L will be described next. Asdescribed already, the uneven structure A is provided on the wafer forLEDs so that the rotation shift angle Θ meets the predetermined range.Herein, the rotation shift angle of an arrangement axis L of the unevenstructure L is not limited particular with respect to the pattern waferfor LEDs, but by meeting the following range, it is possible to moreincrease the internal quantum efficiency IQE and the effect ofsuppressing cracks. In addition, in the following description, therotation shift angle Θ for the arrangement axis A of the unevenstructure A is described as ΘA, and the rotation shift angle Θ for thearrangement axis L of the uneven structure L is described as ΘL.Further, it is possible to define the rotation shift angle ΘL byreplacing the uneven structure A with the uneven structure L and thearrangement axis A with the arrangement axis L to read in the definitiondescription of the rotation shift angle ΘA.

ΔΘ(=|ΘL−ΘA|) that is a difference between the rotation shift angle ΘLand the rotation shift angle ΘA meets a range of 0°≦ΔΘ≦(180/n)°.Particularly, by meeting 0°ΔΘ≦a tan(Duty/2)°, the internal quantumefficiency IQE and the crack suppression effect are further increased.In addition, the Duty is the Duty of the uneven structure. This isbecause the position relationship between the surface formed by thesemiconductor layer when the semiconductor layer grows and the convexportion of the uneven structure L is moderate in adherence of thenucleus of the semiconductor layer, growth and coalescence of growingsemiconductor layer improved by the uneven structure A.

More specifically, since an angle made by the arrangement axis L of theuneven structure L and the surface formed by growth of the semiconductorlayer is decreased, it is possible to reduce stress applied to thegrowing semiconductor layer by the uneven structure L. By this means, itis possible to keep growth properties of the semiconductor layerexcellent, the coalescence of growing semiconductor layers is madeexcellent, dislocations turn and are reduced, and it is possible tosuppress cracks. In the range, by meeting 0°≦ΘL≦a tan(Duty/2)°, theeffects are further exerted, and therefore, such a range is preferable.Particularly, by meeting 0°≦ΘL≦[a tan(Duty/2)°]/2, uniformed is thedensity of convex portions of the uneven structure L that the growingsemiconductor layer passes, it is thereby possible to suppressdisturbance of growth of the semiconductor layer, and therefore, such arange is preferable. From the same effects, it is the most preferable tomeet 0°≦ΘL [a tan(Duty/2)°]/4. On the other hand, by meeting atan(Duty/2)°≦ΔΘ≦(180/n)°, it is considered that it is possible todecrease an amount of particles occurring in chipping the LED. Inmeeting this range, this is because the number of convex portions of theuneven structure L is decreased in viewing from the cleavage directionin chipping the LED. In the range, by meeting atan(Duty/2)°≦ΘL≦(180/n)°, the effects are further exerted, andtherefore, such a range is preferable.

The uneven structure A has substantially the arrangement with n-foldsymmetry, and meets the rotation shift angle Θ as described already. Onthe other hand, the uneven structure L has substantially the arrangementwith m-fold symmetry. The rotation shift angle ΘL with respect to theuneven structure L and the relationship ΔΘ between the rotation shiftangle ΘA and the rotation shift angle ΘL are as described already.Further, the rotation symmetry degree n of the uneven structure A may bethe same as or different from the rotation symmetry degree m of theuneven structure L. In other words, when the combination of the rotationsymmetry degree n of the uneven structure A and the rotation symmetrydegree m of the uneven structure L is described as (n,m), among thecombinations are (6,6), (6,4), (6,2), (4,6), (4,4), (4,2), (2,6), (2,4)and (2,2). Among the combinations, in order to more excellently developthe function of the uneven structure A and the function of the unevenstructure L, (6,6), (4,6), (2,6), (6,2), (4,2) or (2,2) is preferable,and (6,6), (4,6) or (2,6) is the most preferable.

(Uneven Structure L)

The uneven structure L will be described next. The principal function ofthe uneven structure L is to increase the light extraction efficiencyLEE. Therefore, the structure L is preferably a structure foreffectively causing the optical scattering (light scattering or lightdiffraction) phenomenon or the reflection phenomenon, and is capable ofadopting the uneven structure L as described below.

From the viewpoint of effectively developing the optical scatteringproperties (light scattering or light diffraction) or reflection, it ispreferable that the average interval PL of the uneven structure L meetsa range wider than the average interval PA of the uneven structure Ai.e. average interval PL>average interval PA, and concurrently rangesfrom 1000 nm to 100 μm. Particularly, from the viewpoints of morestrongly developing light diffraction properties, and effectivelydisturbing the waveguide mode to increase the light extractionefficiency LEE, the average interval PL is preferably 1200 nm or more,more preferably 1500 nm or more, and most preferably 2000 nm or more. Onthe other hand, from the viewpoints of manufacturing time of the unevenstructure L and a use amount of the semiconductor layer, the upper limitvalue is preferably 50 μm or less, more preferably 20 μm, and mostpreferably 10 μm or less.

The width of the top of the convex-portion of the uneven structure L isnot limited particularly when the uneven structure A is provided onconvex portions 703 of the uneven structure L as shown in FIGS. 27A and27B described later, irrespective of materials of the uneven structureL. This is because the first semiconductor layer grows from the exposedsurface of a wafer 702 for LEDs when materials are different between theuneven structure L and the wafer 702 for LEDs. On the other hand, whenmaterials of the uneven structure L and the wafer 702 for LEDs are thesame, this is because it is possible to reduce dislocations occurringfrom the vertex portion of the convex structure 703 of the unevenstructure L by the uneven structure A. When materials of the unevenstructure L and the wafer 702 for LEDs are the same, from the viewpointsof increasing the internal quantum efficiency IQE and the lightextraction efficiency LEE irrespective of the arrangement of the unevenstructure A with respect to the uneven structure L, as the ratio (widthof the top of the convex-portion/width of the opening part of theconcave-portion) of the width of the top of the convex-portion of theuneven structure L to the width of the opening part of theconcave-portion of the uneven structure L, the ratio is preferablysmaller, and most preferably substantially “0”. In other words, as inthe top of the convex-portion of the uneven structure A, it is the mostpreferable that the top of the convex-portion of the uneven structure Lis also the corner portion with a radius of curvature exceeding “0”. Inaddition, from the study results of the pattern wafer (1) for LEDs, itis conceivable that the corner portion with a radius of curvatureexceeding “0” includes the case where the size of a tabletop is 100 nmor less. In addition, the ratio of “0” means that the width of the topof the convex-portion is 0 nm. However, for example, even when the widthof the top of the convex-portion is measured with the scanning electronmicroscope, it is not possible to accurately measure “0 nm”.Accordingly, the width of the top of the convex-portion herein isassumed to include all cases less than measurement resolution. When theratio (width of the top of the convex-portion/width of the opening partof the concave-portion) is 3 or less, it is possible to keep depositionproperties of the semiconductor layer excellent. This is because it ispossible to decrease an amount of the semiconductor growing from thevertex portion of the convex portion 703 of the uneven structure L.Further, by the ratio being 1 or less, it is possible to increase thelight extraction efficiency LEE. This is because the refractive indexdistribution of the uneven structure L made by the pattern wafer (2) 710for LEDs and the semiconductor layer is suitable from the viewpoint ofthe emitted light. From the viewpoints of significantly increasing boththe internal quantum efficiency IQE and the light extraction efficiencyLEE as described above, the ratio is preferably 0.4 or less, morepreferably 0.2 or less, and further preferably 0.15 or less.

Further, when the materials of the uneven structure L and the wafer 702for LEDs are the same, in the case where the bottom portion of a concaveportion 704 of the uneven structure L has a flat surface, it is possibleto increase the internal quantum efficiency IQE and to decrease adifference between semiconductor deposition apparatuses, and therefore,such a case is preferable. In order to increase the internal quantumefficiency IQE, it is necessary to disperse dislocations inside thesemiconductor layer to decrease local and macroscopic dislocationdensities. Herein, the initial conditions of these physical phenomenaare nucleation and nucleus growth in depositing the semiconductor layerby CVD (Chemical Vapor Deposition), VPE (Vapor Phase Epitaxy) orsputtering. When the bottom portion of the concave portion 704 of theuneven structure L has a flat surface, since it is possible to suitablygenerate nucleation with respect to the bottom portion of the concaveportion of the uneven structure L, growth of the semiconductor layer isstabilized. As a result, it is possible to more increase the internalquantum efficiency IQE.

On the other hand, in the case where the materials of the unevenstructure L and the wafer 702 for LEDs are different from each other,when the uneven structure L is partially provided on the wafer 702 forLEDs i.e. there is the exposed surface on the wafer 702 for LEDs, growthof the first semiconductor layer is achieved. Accordingly, in the casewhere the materials of the uneven structure L and the wafer 702 for LEDsare different from each other, the uneven structure L is comprised aplurality of convex portions provided on the wafer 702 for LEDs and theexposed surface of the wafer 702 for LEDs where the convex portion isnot provided. For example, in using sapphire, SiC, nitridesemiconductor, Si or spinel as the wafer 702 for LEDs, it is possible toprovide the convex portion 703 comprised of one or a mixture of two ormore of metallic aluminium, amorphous aluminium oxide, polycrystallinealuminium oxide, polycrystalline sapphire, silicon nitride (SiO₂),silicon nitride (Si₃N₄), silver (Ag), chromium (Cr), nickel (Ni), gold(Au) and platinum (Pt).

As the Duty of the uneven structure L expressed by the ratio (averagediameter of the bottom of the convex-portion/PL) of the average diameterof the bottom of the convex-portion to the average interval PL of theuneven structure L, from the viewpoint of increasing the lightextraction efficiency LEE, the Duty preferably ranges from 0.03 to 0.83.By the Duty being 0.03 or more, the volume of the convex portion of theuneven structure L is increased to enhance optical scatteringproperties. From the same effect, the ratio is more preferably 0.17 ormore, and most preferably 0.33 or more. On the other hand, by the ratiobeing 0.83 or less, it is possible to increase the area of the bottomportion of the concave portion of the uneven structure L, and it isthereby possible to make excellent adherence of the nucleus of thesemiconductor layer, growth and coalescence of growing semiconductorlayers. By this means, it is possible to increase the internal quantumefficiency IQE. From the same effect, the ratio is more preferably 0.73or less, and most preferably 0.6 or less.

When the aspect ratio of the uneven structure L i.e. average height ofthe uneven structure L/average diameter of the bottom of theconvex-portion of the uneven structure L is 0.1 or more, it is possibleto increase the light extraction efficiency LEE due to the opticalscattering properties by the uneven structure L. Particularly, from theviewpoint of increasing the number of modes of light diffraction, theratio is preferably 0.3 or more, more preferably 0.5 or more, and mostpreferably 0.8 or more. On the other hand, from the viewpoints ofsuppressing cracks and voids in the semiconductor layer, the aspectratio is preferably 5 or less. Further, since it is possible to shortenthe time for preparing the uneven structure L and reduce a use amount ofthe semiconductor, the ratio is more preferably 2 or less, and mostpreferably 1.5 or less.

It is preferable that a height H of the convex portion 703 of the unevenstructure L is two times or less the average interval PL, from theviewpoints of time taken for preparation of the uneven structure L and aused semiconductor crystal amount. Particularly, in the case of theaverage interval PL or less, since the refractive index distribution ofthe uneven structure L is suitable from the viewpoint of the emittedlight, it is possible to more increase the light extraction efficiencyLEE. From this viewpoint, the height H of the uneven structure L is morepreferably 0.8 time or less the average interval PL, and most preferably0.7 time or less.

The relationship between the uneven structure A and the uneven structureL will be described next. The pattern wafer (2) for LEDs of the presentinvention is provided with the uneven structure A having the averageinterval PA meeting the rotation shift angle ΘA described already, andthe uneven structure L having the average interval PL, and the averageinterval PL and the average interval PA are different from each other inthe predetermined ratio range.

Herein, one uneven structure L with a larger average intervalprincipally develops the function of increasing the light extractionefficiency LEE, and the other uneven structure A with a smaller averageinterval principally develops the function of improving the internalquantum efficiency IQE and suppressing cracks. Further, in order for therespective functions of the uneven structures (L and A) to worksynergistically and compensate with/for each other i.e. in order thatthe light extraction efficiency LEE is not decreased by one unevenstructure A for improving the internal quantum efficiency IQE andsuppressing cracks, and that the internal quantum efficiency IQE is notdecreased or cracks do not occur by the other uneven structure L forimproving the light extraction efficiency LEE, it is a feature that theother uneven structure (A or L) is provided on at least a part of thesurface of one uneven structure (L or A). In addition, the rotationshift angle ΘL and ΔΘ are as described already.

FIG. 27 contains cross-sectional schematic diagrams showing an exampleof the pattern wafer (2) for LEDs according to this Embodiment. In thepattern wafer (2) 710 for LEDs shown in FIGS. 27A and 27B, an unevenstructure 720 is provided on the main surface of the wafer 702 for LEDs,and is comprised of a first uneven structure (hereinafter, referred toas uneven structure L) and a second uneven structure (hereinafter,referred to as uneven structure A). The uneven structure L is comprisedof convex portions 703 (or concave portions 704) provided while beingmutually spaced, and concave portions 704 (or convex portions 703)connecting between adjacent convex portions 703 (or concave portions704). A plurality of convex portions 703 (or concave portions 704) hasthe average interval PL.

On the other hand, the uneven structure A is comprised of a plurality ofconvex portions 705 (or concave portions 706) provided on surfaces ofthe convex portions 703 and concave portions 704 constituting the unevenstructure L, and concave portions 706 (or convex portions 705)connecting among the plurality of convex portions 705 (or concaveportions 706). The plurality of convex portions 705 (or concave portions706) has the average interval PA. In FIG. 27A, the uneven structure A isprovided on the vertex-portion surfaces of the plurality of convexportions 703 and the bottom portions of the concave portions 704. On theother hand, in FIG. 27B, the uneven structure A is provided on the topsof the convex portions 703 connecting among a plurality of independentconcave portions 704. In addition, the uneven structure A is not limitedto the examples of FIGS. 27A and 27B, and it is essential only that theuneven structure A is provided on the surface of at least the convexportion 703 or the concave portion 704.

In addition, the uneven structure A meets the rotation shift angle Θ asdescribed already. Further, the uneven structure A preferably meets theshape as described already. Furthermore, the arrangement of the unevenstructure L preferably meets the rotation shift angle ΘL or ΔΘ asdescribed already.

In addition, it is also possible to provide the uneven structure A onthe side surface of the convex portion 703 that connects between theconvex portion 703 and the bottom portion of the concave portion 704. Inthe case where the uneven structure A is provided on the side surface ofthe convex portion 703, it is considered that the effect of disturbingthe waveguide mode is further strengthened, and that it is possible tochange the travelling direction of disturbed emitted light more to thethickness direction of the LED. Therefore, it is made easy to select asealant in packaging the LED.

(Case 1)

Particularly, it is preferable that the uneven structure L is comprisedof a plurality of mutually spaced convex portions 703, and that theuneven structure A is provided on at least bottom portions of theconcave portions 704 of the uneven structure L.

In this case, it is possible to start growth of the semiconductor layerfrom the bottom portion of the concave portion 704 of the unevenstructure L, as a starting point. Particularly, since the unevenstructure A is provided on the bottom portion of the concave portion704, adherence of the nucleus of the semiconductor layer, growth andcoalescence of growing semiconductor layers is made excellent asdescribed already, and it is thereby possible to suppress dislocationsof the semiconductor layer near the uneven structure A, and toconcurrently decrease cracks. Further, since the uneven structure L iscomprised of a plurality of convex portions 703, it is possible tosuppress cracks, near the convex portion 703, of the semiconductor layergrowing from the bottom portion of the concave portion 704. In otherwords, it is possible to increase the internal quantum efficiency IQEand enhance reliability of the LED. Further, as described below, sincethe uneven structures L and A meet the predetermined relationship ofaverage interval, optical scattering properties are increased.Particularly, since there is the configuration that the uneven structureA is provided on at least the bottom portion of the concave portion 704,it is possible to more disturb the waveguide mode by light scattering oroptical reflection, it is possible to suppress re-waveguide of thewaveguide mode, and therefore, the light extraction efficiency LEE isconcurrently increased.

(Case 2)

Further, it is preferable that the uneven structure L is comprised of aplurality of mutually spaced concave portions 704, and that the convexportions 705 or concave portions 706 constituting the uneven structure Aare provided on at least tops of the convex portions 703 of the unevenstructure L.

In this case, it is possible to start growth of the semiconductor layerfrom the vertex portion of the convex portion 703 of the unevenstructure L, as a starting point. Particularly, since the unevenstructure A is provided on the vertex portion of the convex portion 703,it is possible to suppress cracks in the semiconductor layer and toimprove the internal quantum efficiency IQE as described already. Atthis point, growth properties are more excellent in the semiconductorlayer growing from the vertex portion of the convex portion 703 thanthose of the semiconductor crystal growing from the bottom portion ofthe concave portion 704. Therefore, it is possible to block thesemiconductor layer growing from the bottom portion of the concaveportion 704 by the semiconductor layer growing from the vertex portionof the convex portion 703. Accordingly, cracks are suppressed, and theinternal quantum efficiency IQE is effectively increased. Further,depending on the growth condition of the semiconductor layer, it is madeeasy to generate voids inside the concave portion 704. In this case, forexample, when the pattern wafer (2) 710 for LEDs is removed by laserliftoff, removal accuracy is enhanced. Further, as described below,since the uneven structures L and A meet the predetermined relationshipof average interval, optical scattering properties are increased.Particularly, since the uneven structure L is comprised of a pluralityof concave portions 704, the volume change is more increased, the effectof disturbing the waveguide mode is increased, and the light extractionefficiency LEE is enhanced.

In the pattern wafer (2) 710 for LEDs according to this Embodimentdescried as the above-mentioned cases 1 and 2, it is preferable that thecoverage of the uneven structure A to the uneven structure L exceeds 0%and is less than 100%.

In this case, since the uneven structure A is necessarily provided onthe convex portion 703 or concave portion 704 of the uneven structure L,from the above-mentioned principles, the internal quantum efficiency IQEis effectively increased, and it is possible to suppress cracks insidethe semiconductor layer. On the other hand, all of the convex portions703 and concave portions 704 of the uneven structure L are not embeddedby the uneven structure A. By this means, it is possible to suppressdegradation of the effect of increasing the light extraction efficiencyLEE due to the uneven structure L by the uneven structure A. In otherwords, the effect of concurrently increasing the internal quantumefficiency IQE and the light extraction efficiency LEE is furtherenhanced.

(Case 3)

FIG. 27C is a cross-sectional schematic diagram showing another exampleof the pattern wafer (2) for LEDs. In the pattern wafer (2) 710 forLEDs, the uneven structure 720 is provided on the main surface of thewafer 702 for LEDs, and is comprised of a first uneven structure(hereinafter, referred to as uneven structure A) and a second unevenstructure (hereinafter, referred to as uneven structure L). The unevenstructure A is comprised of mutually spaced convex portions 705, andconcave portions 706 connecting between adjacent convex portions 705. Aplurality of convex portions 705 has the average interval PA.

On the other hand, the uneven structure L is comprised of a plurality ofconvex portions 703, which are provided apart from one another on thesurface of the uneven structure A to expose a part of the unevenstructure A and are provided on the surfaces of the convex portions 705and concave portions 706 constituting the uneven structure A. Theplurality of convex portions 703 has the average interval PL.

The ratio, which is between the average interval PL of the unevenstructure L and the average interval PA of the uneven structure A of thepattern wafer (2) 710 for LEDs described with reference to FIGS. 27B and27C, exceeds 1 and is 2000 or less. By the ratio exceeding 1 and being2000 or less, it is possible to deposit the semiconductor layer withcracks suppressed and the internal quantum efficiency IQE increased, andto increase the light extraction efficiency LEE. Particularly, from theviewpoint of increasing the difference between the average interval PLand the average interval PA, and suppressing an obstacle to the lightextraction efficiency LEE by the uneven structure A and an obstacle tothe internal quantum efficiency IQE by the uneven structure L, the ratio(PL/PA) is preferably 1.1 or more, more preferably 1.5 or more, andfurther preferably 2.5 or more. Further, from the viewpoints ofincreasing processing resolution of the uneven structure A, moreincreasing the internal quantum efficiency IQE, and suppressing cracks,the ratio (PL/PA) is preferably 5.5 or more, more preferably 7.0 ormore, and most preferably 10 or more. On the other hand, from theviewpoints of increasing optical scattering properties (lightdiffraction or light scattering) due to the uneven structure A, andachieving improvements in internal quantum efficiency IQE due to theuneven structure A and improvements in light extraction efficiency LEEdue to the uneven structure L and uneven structure A, the ratio (PL/PA)is preferably 700 or less, more preferably 300 or less, and furtherpreferably 100 or less. Further, from the viewpoints of reducing stressapplied to the semiconductor layer from the uneven structure L to moresuppress cracks, increasing the volume change of the uneven structure L,increasing the density of the uneven structure A, and enhancingprocessing accuracy of the uneven structure L and the uneven structureA, the ratio (PL/PA) is preferably 50 or less, more preferably 40 orless, and further preferably 30 or less.

As the epitaxial wafer for LEDs using the pattern wafer (2) for LEDs andLED chip, it is possible to adopt the same states as in the case ofusing the pattern wafer (1) for LEDs. In this case, the uneven structure720 comprised of the uneven structure L and the uneven structure A ofthe pattern wafer (2) for LEDs is capable of being replaced with theuneven structure 20 of the pattern wafer (1) for LEDs to read.

Concerning the pattern wafer (2) for LEDs, the ratio (Hbun/Have) of thedistance (Hbun) between the surface on the light emitting semiconductorlayer side and the surface on the first semiconductor layer side of thelight emitting semiconductor layer to the average height (Have) of theuneven structure A corresponds to the ratio (Hbun/Have) as described inthe pattern wafer (1) for LEDs.

Concerning the pattern wafer (2) for LEDs, the ratio (Hbu/Have) of thedistance (Hbu) between the surface on the light emitting semiconductorlayer side of the pattern wafer (2) for LEDs and the surface on thedoped first semiconductor layer side of the undoped first semiconductorlayer to the average height (Have) of the uneven structure A correspondsto the ratio (Hbu/Have) as described in the pattern wafer (1) for LEDs.

As the shape of the uneven structure AL, for example, it is possible toadopt the line-and-space structure with a plurality of bar-shaped bodiesarranged, lattice structure with a plurality of bar-shaped bodiescrossing, dot structure with a plurality of dot(convex portion,protrusion)-shaped structures arranged, hole structure with a pluralityof hole(concave portion)-shaped structures arranged, and the like. Asthe dot structure and hole structure, examples thereof are a cone,cylinder, quadrangular pyramid, quadrangular prism, hexagonal pyramid,hexagonal prism, n-gonal pyramid (n≧3), n-gonal prism (n≧3), the shapeof a caldera, the shape of a double ring, and the shape of a multi-ring.Herein, the shape of a caldera refers to the shape obtained by bringingthe front end of a large cone into contact with the front end of a smallhollow cone, and subsequently, pressing the small cone into the largecone, and is also called the volcano type. In addition, these shapesinclude shapes that the outside diameter of the bottom is distorted, thecorner portion of the bottom portion of the n-gon has a radius ofcurvature exceeding “0” and is rounded, the side surface is curved, andthat the vertex portion has a radius of curvature exceeding “0” and isrounded.

In addition, the dot structure is a structure where a plurality ofconvex portions is arranged independently of one another. That is, eachconvex portion is separated by a continuous concave portion. Inaddition, convex portions may be smoothly connected by the continuousconcave portion. On the other hand, the hole structure is a structurewhere a plurality of concave portions is arranged independently of oneanother. That is, each concave portion is separated by a continuousconvex portion. In addition, concave portions may be smoothly connectedby the continuous convex portion.

For selecting the dot structure or selecting the hole structure, it ispossible to select as appropriate according to the apparatus used inmanufacturing the epitaxial wafer for LEDs and use of the LED.Particularly, in an environment for giving priority to suppression ofcracks and improvements of the internal quantum efficiency IQE, theuneven structure L is preferably the dot-shaped structure. This isbecause it is possible to induce Epitaxial Lateral Overgrowth of thesemiconductor layer, while suppressing cracks in the top of theconvex-portion, and increase the internal quantum efficiency IQE alsodue to the uneven structure L with a large average interval PL. On theother hand, in an environment for particularly increasing the lightextraction efficiency LEE, the uneven structure AL is preferably thehole structure. In the case of hole structure, this is because a changeof the refractive index viewed from the semiconductor layer is suitablefor optical scattering properties. In addition, the combination (unevenstructure L, uneven structure A) of the uneven structure L and unevenstructure A may be one of (dot structure, dot structure), (holestructure, hole structure), (dot structure, hole structure), and (holestructure, dot structure).

Described next are the uneven structure A and uneven structure Lconstituting the uneven structure 720.

FIG. 28 contains cross-sectional schematic diagrams showing anotherexample of the pattern wafer (2) for LEDs according to this Embodiment,and is the case of including the (Case 1) and (Case 2) described withreference to FIGS. 27A and 27B. As shown in FIGS. 28A to 28C, the unevenstructure L with a large volume change is provided on the surface of thepattern wafer (2) 710 for LEDs, and the uneven structure A with a largestructure density is provided on surfaces of at least either the convexportions 703 or the concave portions 704 constituting the unevenstructure L. By adopting such a configuration, it is possible toincrease the internal quantum efficiency IQE, while decreasing cracksdue to the uneven structure A, and to increase the light extractionefficiency LEE by optical scattering properties (light diffraction orlight scattering) due to the uneven structure L. FIGS. 28A to 28C showarrangement examples of the uneven structure A with respect to theuneven structure L.

Particularly, as shown in FIG. 28A, it is preferable that the firstuneven structure L is comprised of a plurality of mutually spaced convexportions 703, and that the convex portions 705 or concave portions 706constituting the uneven structure A are provided on at least bottomportions of the concave portions 704 of the first uneven structure L.

In this case, as described already in the (Case 1) and (Case 2), sinceit is possible to start growth of the semiconductor layer from thebottom portion of the concave portion 704 of the uneven structure L as astarting point, the internal quantum efficiency IQE is increased, and itis possible to suppress cracks. Further, it is possible to enhancereliability of the LED. Furthermore, as described already, since theuneven structures L and A meet the predetermined relationship of averageinterval, optical scattering properties are increased. Particularly,since there is the configuration that the uneven structure A is providedon at least the bottom portion of the concave portion 704, it ispossible to more disturb the waveguide mode by light scattering oroptical reflection, it is possible to suppress re-waveguide of thewaveguide mode, and therefore, the light extraction efficiency LEE isconcurrently increased.

Alternatively, as shown in FIG. 28B, it is preferable that the unevenstructure L is comprised of a plurality of mutually spaced concaveportions 704, and that the convex portions 705 or concave portions 706constituting the uneven structure A are provided on at least tops of theconvex portions 703 of the uneven structure L.

In this case, as described already in the (Case 1) and (Case 2), it ispossible to start growth of the semiconductor layer from the vertexportion of the convex portion 703 of the uneven structure L as astarting point. Accordingly, it is possible to effectively reducedislocations of the semiconductor layer growing from the vertex portionof the convex portion 703 and to suppress cracks. Further, since it ismade easy to generate voids inside the concave portion 704, for example,when the pattern wafer (2) 710 for LEDs is removed by laser liftoff,removal accuracy is enhanced. Furthermore, since the uneven structures Land A meet the predetermined relationship of average interval, opticalscattering properties are increased. Particularly, since the unevenstructure L is comprised of a plurality of concave portions 704, thevolume change is more increased, the effect of disturbing the waveguidemode is increased, and the light extraction efficiency LEE is enhanced.

In addition, in the case where the uneven structure A is provided on thesurfaces of both the convex portions 703 and the concave portions 704 ofthe uneven structure L as shown in FIG. 28C, it is possible to achieveboth of the effects described with reference to FIGS. 28A and 28B.

In the pattern wafer (2) 710 for LEDs as described above, it ispreferable that the coverage of the uneven structure A to the unevenstructure L exceeds 0% and is less than 100%.

In this case, since the uneven structure A is necessarily provided onthe convex portion 703 or concave portion 704 of the uneven structure L,from the above-mentioned principles, the internal quantum efficiency IQEis effectively increased, and cracks are suppressed. On the other hand,all of the convex portions 703 and concave portions 704 are not embeddedby the uneven structure A. By this means, it is possible to suppressdegradation of the effect of increasing the light extraction efficiencyLEE due to the uneven structure L by the uneven structure A. In otherwords, it is possible to concurrently increase the internal quantumefficiency IQE and the light extraction efficiency LEE, and to suppresscracks.

Particularly, from the viewpoints of suppressing increases in roughnessof the surface of the uneven structure L, and increasing the effect dueto the uneven structure L of disturbing the travelling direction ofemitted light forming the waveguide mode inside the semiconductor layer,the coverage is preferably 90% or less, more preferably 80% or less, andmost preferably 50% or less. Further, from the viewpoint of exerting theeffect of increasing the internal quantum efficiency IQE due to theuneven structure A, decreasing a use amount of the semiconductor layer,and enhancing productivity of LEDs, the coverage is preferably 0.01% ormore, more preferably 0.1% or more, and most preferably 0.15% or more.In addition, in the case of particularly more increasing the internalquantum efficiency IQE, within the above-mentioned widest range, thecoverage preferably ranges from 50% to 90%, more preferably ranges from60% to 86%, and most preferably ranges from 70% to 84%. In the case ofmeeting these ranges, it is possible to most effectively develop theeffects due to the uneven structure A. On the other hand, in the case ofintending to particularly increase the light extraction efficiency LEE,within the above-mentioned widest range, the coverage is preferably in arange of 0.1% to 30%, more preferably in a range of 0.1% to 10%, andmost preferably in a range of 0.1% to 5%. By meeting these ranges, sinceit is possible to prevent the emitted light with the waveguide modedisturbed from forming again the waveguide mode, and therefore, thelight extraction efficiency is more increased.

Herein, the coverage is a plane occupancy rate of the convex portion 705or concave portion 706 of the uneven structure A with respect to thesurface of the convex portion 703 or concave portion 704 of the unevenstructure L. In other words, in the case of observing some convexportion 703 from the top surface side and assuming that S is a planearea of the convex portion 703 and the concave-portion 704 surroundingthe circumference of the contour of the convex portion 703, assumingthat Si is a total plane area of the convex portions 705 or concaveportions 706 of the uneven structure A inside the observation image, thecoverage is (Si/S)×100.

FIG. 29 contains schematic diagram illustrating uneven structures in thepattern wafer (2) for LEDs according to this Embodiment. FIG. 29A showsthe case where the uneven structure L is comprised of a plurality ofindependent convex portions 703, and particularly, shows the case theuneven structure A is provided on the bottom portion of the concaveportion 704. Alternatively, the case is shown where the uneven structureL is provided on the surface of the uneven structure A to partiallyexpose the uneven structure A. In this example, each of the contourshape of the bottom portion of the convex portion 703 and the contourshape of the bottom portion of the convex portion 705 is circular. It isassumed that S is the area of the convex portion 703 in a plane imageobtained by observing from the vertex portion side of the convex portion703, and the concave portion 704 surrounding the circumference of thecontour of the convex portion 703. Herein, the area S is an area of apolygon 841 made by joining vertex-portion center portions of otherconvex portions 703 adjacent to some convex portion 703. By assumingthat Si is the total area of areas made by contours of the bottomportions of convex portions 705 of the uneven structure A includedinside the area A, or the total area of opening portions of concaveportions 706, the coverage is given as Si/S×100. In addition, FIG. 29Aexemplifies the case where the uneven structure A is disposed on onlythe bottom of the concave-portion of the uneven structure L, but thearrangement of the uneven structure A is not limited thereto asdescribed already. Similarly, FIG. 29B shows the case where the unevenstructure L is comprised of a plurality of independent concave portions704, and particularly, the uneven structure A is provided on the topsurface of the convex portion 703. In this example, the opening shape ofthe concave portion 704 and the contour shape of the bottom portion ofthe convex portion 703 are circular. It is assumed that S is the area ofthe concave portion 704 in a plane image obtained by observing from thevertex portion side of the convex portion 703, and the convex portion703 surrounding the circumference of the contour of the concave portion704. Herein, the area S is an area of a polygon 841 made by joiningopening-portion center portions of other concave portions 704 adjacentto some concave portion 704. By assuming that Si is the total area ofareas made by contours of the bottom portions of convex portions 705 ofthe uneven structure A included inside the area A, or the total area ofopening portions of concave portions 706, the coverage is given asSi/S×100. In addition, FIG. 29B exemplifies the case where the unevenstructure A is disposed on only the vertex portion of the convex portion703 of the uneven structure L, but the arrangement of the unevenstructure A is not limited thereto as described already.

In addition, as shown in FIG. 29B, in the case where the unevenstructure A is disposed on only the vertex-portion top surface of theconvex portion 703 of the uneven structure L, by assuming that ST is thearea of the vertex-portion top surface of the convex portion 703 inobserving from the vertex portion side of the convex portion 703, andthat SiT is the total plane area of the uneven structure A includedinside the vertex-portion top surface of the convex portion 703 havingthe area ST, it is possible to obtain coverage (SiT/ST×100). Inaddition, this coverage is called the coverage T with respect to thevertex-portion top surface of the convex portion 703.

Similarly, as shown in FIG. 29A, in the case where the uneven structureA is disposed on only the bottom surface of the concave portion 704 ofthe uneven structure L, by assuming that SB is the area of the bottomsurface of the concave portion 704 in observing from the vertex portionside of the convex portion 705, and that SiB is the total plane area ofthe uneven structure A included inside the bottom surface of the concaveportion 704 having the area SB, it is possible to obtain coverage(SiB/SB×100). In addition, this coverage is called the coverage B withrespect to the bottom surface of the concave portion 704.

Each of the coverage T with respect to the vertex-portion top surface ofthe convex portion 703 and the coverage B with respect to the bottomsurface of the concave portion 704 preferably ranges from 1% to 90%.Particularly, from the viewpoints of excellently increasing the internalquantum efficiency IQE and enhancing light emission output of the LED,each of the coverage T with respect to the vertex-portion top surface ofthe convex portion 703 and the coverage B with respect to the bottomsurface of the concave portion 704 preferably ranges from 3% to 60%,more preferably ranges from 5% to 55%, and most preferably ranges from10% to 40%. Further, also when the uneven structure A is provided on thevertex portion of the convex portion 703, side surface of the convexportion 703 and bottom portion of the concave portion 704 of the unevenstructure L, it is preferable that a coverage of the uneven structure Awith respect to the vertex-portion top surface of the convex portion 703of the uneven structure L or a coverage of the uneven structure A withrespect to the bottom surface of the concave portion 704 of the unevenstructure L meets the coverage T with respect to the vertex-portion topsurface of the convex portion 703 or the coverage B with respect to thebottom surface of the concave portion 704, respectively.

In addition, in the uneven structure L, when a plurality of convexportions 703 is separately provided on the wafer 702 for LEDs, theuneven structure L is comprised of the main surface of the wafer 702 forLEDs and the plurality of convex portions 703. In this case, theplurality of convex portions 703 corresponds to convex portions of theuneven structure L, and exposed portions, between convex portions 703,of the main surface of the wafer 702 for LEDs correspond to the concaveportions 704 of the uneven structure L.

On the other hand, when the uneven structure L is provided by directlyprocessing the wafer 702 for LEDs, materials of the uneven structure Land the wafer 702 for LEDs are the same.

FIG. 28A is the case where the uneven structure L is comprised of aplurality of independent convex portions 703, and the uneven structure Ais provided on the surfaces of the concave portions 704 of the unevenstructure L. FIG. 28B is the case where the uneven structure L iscomprised of a plurality of independent convex portions 703, and theuneven structure A is provided on the surfaces of the convex portions703 of the uneven structure L. FIG. 28C is the case where the unevenstructure L is comprised of a plurality of independent convex portions703, and the uneven structure A is provided on the surfaces of theconvex portions 703 and concave portions 704 of the uneven structure L.In addition, concerning FIGS. 28A to 28C, the shape of the vertexportion of the convex portion 703 of the uneven structure L is drawn inthe rounded shape, and as described already, it is also possible to makethe shape of the vertex portion of the convex portion 703 of the unevenstructure L in the shape of a tabletop and the like.

As shown in FIG. 28A, since the uneven structure A is provided on theconcave portions 704 of the uneven structure L, it is possible toexcellently increase the internal quantum efficiency IQE. Further, sincethe concavo-convex L is comprised of a plurality of convex portions 703,the effect of suppressing cracks is increased in the semiconductorlayer. This is because growth of the semiconductor layer starts from theconcave portion 704 of the uneven structure L. In other words, adherenceof the nucleus of the semiconductor layer, growth and coalescenceproperties of growing semiconductor layers are made excellent due to theuneven structure A, the semiconductor layer with excellent growthproperties grows from the concavo portion 704 of the uneven structure L,and it is thereby possible to suppress dislocations in the concaveportion 704 of the uneven structure L. In addition, in FIG. 28A, theuneven structure A is not drawn on the side surface portion of theconvex portion 703, but it is also possible to provide the unevenstructure A on side surface portion of the convex portion 703. In thiscase, it is considered that the effect of disturbing the waveguide modeis further strengthened, and that it is possible to change thetravelling direction of disturbed emitted light more to the thicknessdirection of the LED. Therefore, it is made easy to select a sealant inpackaging the LED.

When the uneven structure L is comprised of the same material as that ofthe wafer 702 for LEDs, in order to suppress dislocations occurring fromthe vertex portion of the convex portion 703 of the uneven structure L,such a structure is preferable that the diameter of the convex portion703 of the uneven structure L decreases from the bottom portion to thevertex portion. Particularly, preferable is a structure that the vertexportion of the convex portion 703 of the uneven structure L continuouslyconnects to the side surface portion of the convex portion 703 of theuneven structure L i.e. a structure that the vertex portion of theconvex portion is comprised of the corner portion with a radius ofcurvature exceeding “0”. The uneven structure L is capable of adoptingshapes such as the shape of a disk, shape of a cone, the shape of ann-gonal prism (n≧3) and the shape of an n-gonal pyramid (n≧3), and amongthe shapes, from the viewpoints of enhancing uniformity of growth of thefirst semiconductor layer and more reducing cracks and dislocationsoccurring inside the first semiconductor layer, preferable is one of theshape of a cone, the shape of a disk, the shape of a triangular prism,the shape of a triangular pyramid, the shape of a hexagonal prism andthe shape of a hexagonal pyramid. In addition, the vertex portion of thepyramid may be a corner portion with a radius of curvature of “0” or arounded corner portion with a radius of curvature exceeding “0”.Particularly, in the case of the shape of a pyramid, by having thecorner portion with a radius of curvature exceeding “0”, it is possibleto suppress cracks occurring in growth of the semiconductor layer, andtherefore, long-term reliability of the LED is enhanced. Particularly,in these shapes, it is preferable that the tilt angle of the sidesurface portion of the convex portion 703 has change points ranging from1 to 5. In addition, the number of points more preferably ranges from 1to 3. Further, instead of a liner shape, the side surface portion of theconvex portion 703 may be in the shape having a bulge.

On the other hand, when the uneven structure L and the wafer 702 forLEDs are comprised of different materials, as well as shapes such as theshape of a cone and the shape of an n-gonal pyramid (n≧3), the convexportion 703 of the uneven structure L may be of structure such as theshape of a disk and the shape of an n-gonal prism (n≧3) where the tiltangle of the side surface portion of the convex portion 703 issubstantially a right angle with respect to the surface forming thebottom portion of the convex portion 703. Particularly, from theviewpoints of enhancing uniformity of growth of the first semiconductorlayer, and reducing cracks and dislocations occurring inside the firstsemiconductor layer, preferable is one of the shape of a cone, the shapeof a disk, the shape of a triangular prism, the shape of a triangularpyramid, the shape of hexagonal prism and the shape of a hexagonalpyramid. Further, from the viewpoint of suppressing cracks occurringinside the first semiconductor layer such a structure is preferable thatthe diameter of the convex portion 703 of the uneven structure Ldecreases from the bottom portion to the vertex portion. Particularly,in these shapes, it is preferable that the tilt angle of the sidesurface portion of the convex portion 703 has change points ranging from1 to 5. In addition, the number of points more preferably ranges from0.1 to 3. Further, instead of a liner shape, the side surface portion ofthe convex portion 703 may have a shape having a bulge. In addition,when the uneven structure L and the wafer 702 for LEDs are comprised ofdifferent materials, as an absolute value |nL−ns| of a differencebetween the refractive index nL of the uneven structure L and therefractive index ns of the wafer 702 for LEDs, the absolute value ispreferably 0.1 or more. By meeting such a range, it is possible toincrease the optical presence of the uneven structure L viewed from thesemiconductor layer. In other words, since optical scattering propertiesare increased, the effect of disturbing the waveguide mode is increased.Furthermore, it is made easy to design light extraction from the sidesurface direction of the LED or light extraction from the top surfacedirection.

As shown in FIG. 28B, since the uneven structure A is provided on theconvex portions 703 of the uneven structure L, even when a flat surfaceexists on the vertex portion of the convex portion 703 of the unevenstructure L, it is possible to excellently increase the internal quantumefficiency IQE. This is because growth of the semiconductor layer startsfrom the flat surface of the uneven structure L. In other words, sinceadherence of the nucleus of the semiconductor layer and growth is madeexcellent on the flat surface of the vertex portion of the convexportion 703 of the uneven structure L, and coalescence of growingsemiconductor layers is also made excellent, cracks are suppressed, thecollision of dislocations increases, and the internal quantum efficiencyIQE is enhanced. Further, with respect to the semiconductor layergrowing from the bottom portion of the concavo portion 704 of the unevenstructure L, it is possible to reduce dislocations by Epitaxial LateralOvergrowth of the semiconductor layer. Alternatively, by thesemiconductor layer growing from the vertex portion of the convexportion 703 of the uneven structure L, it is possible to inhibit growthof the semiconductor layer growing from the concave portion 704 of theuneven structure L. Accordingly, the dislocation density of thesemiconductor layer is decreased, and it is possible to increase theinternal quantum efficiency IQE. In this case, in order to promotegrowth of the semiconductor layer, it is preferable that the bottomportion of the concave portion 704 of the uneven structure L has a flatsurface. Further, such a structure is preferable that the vertex portionof the convex portion 703 of the uneven structure L is smaller than thebottom portion. Further, from the viewpoints of keeping the internalquantum efficiency IQE excellent due to the uneven structure A, it ispreferable that the uneven structure A is the dot structure comprised ofa plurality of convex portions 705, and that the bottom portion of theconcave portion 706 of the uneven structure A has a flat surface.Furthermore, in the structure that the diameter of the convex portion703 of the uneven structure A decreases from the bottom portion to thevertex portion, dislocation dispersion is more promoted, and therefore,such a structure is preferable. The uneven structure L is capable ofadopting shapes such as the shape of a disk, shape of a cone, the shapeof an n-gonal prism (n≧3) and the shape of an n-gonal pyramid (n≧3), andamong the shapes, from the viewpoints of enhancing uniformity of growthof the first semiconductor layer and reducing cracks and dislocationsoccurring inside the first semiconductor layer, preferable is one of theshape of a cone, the shape of a disk, the shape of a triangular prism,the shape of a triangular pyramid, the shape of a hexagonal prism andthe shape of a hexagonal pyramid. In addition, the vertex portion of thepyramid may be a corner portion with a radius of curvature of “0” or arounded corner portion with a radius of curvature exceeding “0”.Particularly, in the case of the shape of a pyramid, by having thecorner portion with a radius of curvature exceeding “0”, it is possibleto suppress cracks occurring in growth of the semiconductor layer, andtherefore, long-term reliability of the LED is enhanced. Particularly,in these shapes, it is preferable that the tilt angle of the sidesurface portion of the convex portion 703 has change points ranging from1 to 5. In addition, the number of points more preferably ranges from 1to 3. Further, instead of a liner shape, the side surface portion of theconvex portion 703 may be in the shape having a bulge. Furthermore, whenthe uneven structure A is provided on the convex-portion 703 vertexportion of the uneven structure L, for example, it is made easy toremove the pattern wafer (2) 710 for LEDs by laser liftoff, and it isthereby possible to increase the emission intensity per charged power ofthe LED.

By the structure as shown in FIG. 28C, it is possible to combine theeffects developed by the structures of FIGS. 28A and 28B as describedabove.

FIG. 28 exemplifies the case where the uneven structure L is comprisedof a plurality of independent convex portions 703, and the unevenstructure L may be comprised of a plurality of independent concaveportions 704.

FIG. 30 contains cross-sectional schematic diagrams showing anotherexample of the pattern wafer (2) for LEDs according to this Embodiment.FIG. 30A is the case where the uneven structure L is comprised of aplurality of independent concave portions 704, and the uneven structureA is provided on the surfaces of the convex portions 703 of the unevenstructure L. FIG. 30B is the case where the uneven structure L iscomprised of a plurality of independent concave portions 704, and theuneven structure A is provided on the surfaces of the concave portions704 of the uneven structure L. FIG. 30C is the case where the unevenstructure L is comprised of a plurality of independent concave portions704, and the uneven structure A is provided on the surfaces of theconvex portions 703 and concave portions 704 of the uneven structure L.

As shown in FIG. 30A, since the uneven structure A is provided on theconvex portions 703 of the uneven structure L, it is possible toexcellently increase the internal quantum efficiency IQE. Further, sincethe uneven structure L is comprised of a plurality of independentconcave portions 704, it is made easy to form voids inside the concaveportion 704 of the uneven structure L. In this case, removal accuracy bylaser liftoff is enhanced in the pattern wafer (2) for LEDs. Further,when voids are formed, the difference in the refractive index issignificantly increased between the semiconductor layer and the void,and therefore, the degree of increases in light extraction efficiencyLEE is sharply increased. This is the same as in the uneven structureshown in FIG. 30B or 30C.

As described above, the principal function of the uneven structure A isto improve the internal quantum efficiency IQE and suppress cracks.Therefore, it is preferable that the material of the uneven structure Ais the same as the material constituting the wafer 702 for LEDs. On theother hand, the principal function of the uneven structure L is toimprove the light extraction efficiency LEE. Therefore, the material ofthe uneven structure L may be the same as or different from the materialconstituting the wafer 702 for LEDs. Examples thereof are a case whereboth the uneven structure A and the uneven structure L are comprised ofsapphire, SiC (silicon carbide), nitride semiconductor, Si (silicon) orspinel, and another case where the uneven structure A is comprised ofsapphire, SiC, nitride semiconductor, Si or spinel, and the unevenstructure L is one or a mixture of two or more of metal aluminium,amorphous aluminium oxide, polycrystalline aluminium oxide,polycrystalline sapphire, silicon oxide (SiO₂), silicon nitride (Si₃N₄),silver (Ag), chromium (Cr), nickel (Ni), gold (Au) and platinum (Pt).

FIG. 27C is a cross-sectional schematic diagram showing another exampleof the pattern wafer (2) for LEDs. As shown in FIG. 27C, the unevenstructure A with a high structure density is provided on the surface ofthe pattern wafer (2) 710 for LEDs, and the uneven structure L with alarge volume change is provided on at least a part of the surface of theuneven structure A. More specifically, the uneven structure A comprisedof pluralities of convex portions 705 and concave portions 706 is formedon the main surface of the wafer 702 for LEDs, and further, a pluralityof convex portions 703 is formed apart from one another to expose a partof the surface of the uneven structure A to constitute the unevenstructure L.

By such a configuration, it is possible to improve cracks and increasethe internal quantum efficiency IQE due to the uneven structure Aexposed between convex portions 703 constituting the uneven structure L,and it is thereby possible to increase the light extraction efficiencyLEE by optical scattering properties (light diffraction or lightscattering) due to the uneven structure L.

As shown in FIG. 27C, since the uneven structure L is provided on a partof the surface of the uneven structure A, it is possible to increase theinternal quantum efficiency IQE and increase the light extractionefficiency LEE. This is because adherence of the nucleus of thesemiconductor layer, growth and coalescence of growing semiconductorlayers is made excellent due to the uneven structure A, the collision ofdislocations excellently occurs to increase the internal quantumefficiency IQE, it is possible to disperse the coalescence portions, andit is thereby possible to suppress cracks. Further, this is because itis possible to disturb the waveguide mode by optical scatteringproperties due to the uneven structure L.

When the material of the uneven structure L is different from thematerial of the wafer 702 for LEDs, the uneven structure L may astructure such as the shape of a disk and the shape of an n-gonal prism(n≧3) where the width of the top of the convex-portion is substantiallythe same as the width of the bottom of the convex-portion. Particularly,from the viewpoint of more excellently suppressing cracks occurringinside the first semiconductor layer, such a structure is preferablethat the width of the top of the convex-portion of the uneven structureL is smaller than the width of the bottom of the convex-portion of theuneven structure L.

On the other hand, when materials of the uneven structure L and thewafer 702 for LEDs are the same, in order to suppress dislocationsoccurring from the vertex portion of the convex portion 703 of theuneven structure L, such a structure is preferable that the vertexportion of the convex portion 703 of the uneven structure L is smallerthan the bottom portion thereof. Particularly, preferable is a structurewhere the vertex portion of the convex portion 703 of the unevenstructure L is continuously connected to the side surface portionthereof i.e. structure where the width of the top of the convex-portionis close to “0”. In addition, from the study in the pattern wafer (1)for LEDs, it is also conceivable that the expression that the width ofthe top of the convex-portion is close to “0” is capable of beinginterpreted as including the case where the size of the tabletop is 100nm or less.

Further, from the viewpoint of more increasing the internal quantumefficiency IQE also due to the uneven structure L, the uneven structureL is preferably the dot structure comprised of a plurality of convexportions 703. This is because it is possible to reduce dislocationsinside the semiconductor layer growing from the concave portion 704provided between the convex portions 703 by Epitaxial LateralOvergrowth. From the same effect, it is preferable that the width of thetop of the convex-portion of the uneven structure L is smaller than thewidth of the bottom of the convex-portion.

On the other hand, from the viewpoint of more increasing the internalquantum efficiency IQE, it is preferable that the uneven structure A isthe dot structure comprised of a plurality of convex portions 705 andthat the bottom portion of the concave portion 706 of the unevenstructure A has a flat surface. Further, in a structure where the widthof the top of the convex-portion of the uneven structure A is smallerthan the width of the bottom of the convex-portion, dislocationdispersion is more promoted, and therefore, such a structure ispreferable.

As described above, the principal function of the uneven structure A isto improve the internal quantum efficiency IQE. Therefore, it ispreferable that the material of the uneven structure A is the materialconstituting the wafer 702 for LEDs. On the other hand, the principalfunction of the uneven structure L is to improve the light extractionefficiency LEE. Therefore, the material of the uneven structure L may bethe same as or different from the material of the wafer 702 for LEDs.

By using the pattern wafer (2) 710 for LEDs according to thisEmbodiment, from the principles described already, it is possible toobtain the semiconductor layer with cracks suppressed and high internalquantum efficiency IQE. Further, the LED chip exhibits high lightextraction efficiency LEE. In other words, while efficiently emittinglight, it is possible to effectively extract the emitted light to theoutside of the LED chip, and it is possible to enhance reliability ofthe LED chip. Therefore, in the LED device manufactured using thepattern wafer (2) 710 for LEDs according to this Embodiment, a heatingvalue is small. By the heating value being small, it is meant thatlong-term stability of the LED device is not only increased, and that itis also possible to reduce a load (for example, provision of excessiveradiating members) according to measures for heat dissipation.

As materials constituting the uneven structure when materials of thewafer 702 for LEDs and the uneven structure are different from eachother, for example, it is possible to use the materials of the wafer 702for LEDS as described above, and one or a mixture of two or more ofmetal aluminium, amorphous aluminium Oxide, polycrystalline aluminiumoxide, polycrystalline sapphire, silicon oxide (SiO₂), silicon nitride(Si₃N₄), silver (Ag), chromium (Cr), nickel (Ni), gold (Au) and platinum(Pt).

<<Manufacturing Method of the Pattern Wafer (2) for LEDs>>

Described next are manufacturing methods of the pattern wafer (2) 710for LEDs according to this Embodiment of the present invention.

As long as the pattern wafer (2) 710 for LEDs according to thisEmbodiment is provided with the uneven structure meeting theabove-mentioned conditions, manufacturing methods thereof are notlimited, and it is possible to manufacture by the same manufacturingmethod as that of the pattern wafer (1) for LEDs.

In the case of the pattern wafer (2) 710 for LEDs, it is possible tomanufacture the uneven structure 720 by preparing the uneven structureL, and next, preparing the uneven structure A. The manufacturing methodsof the uneven structure L are capable being sorted into two.

(1) The Case of Directly Processing the Wafer for LEDs to Provide theUneven Structure L

As the method of directly processing the wafer 702 for LEDs to providethe uneven structure L, it is possible to manufacture by the transfermethod, photolithography method, thermal lithography method, electronbeam lithography method, interference exposure method, lithographymethod using nanoparticles as a mask, lithography method using aself-organizing structure as a mask and the like. Particularly, from theviewpoints of processing accuracy and processing speed of the unevenstructure of the wafer 702 for LEDs, it is preferable to adopt thephotolithography method or the transfer method. In addition, as theetching method, either of wet etching and dry etching is preferable.Particularly, in the case of precisely controlling the plane directionof the side surface of the convex portion of the uneven structure L, wetetching is preferable. On the other hand, from the viewpoint ofprecision control of the shape of the uneven structure L, the dryetching method is preferable, and it is possible to adopt the dryetching method as described in the pattern wafer (1) for LEDs. Thetransfer method is as described in the pattern wafer (1) for LEDs.

(2) The Case of Providing the Uneven Structure L Separately on the Waferfor LEDs

As the method of providing the uneven structure L separately on thewafer 702 for LEDs, among the methods are the transfer method, a methodof forming a thin film with particles included therein on the wafer 702for LEDs, and subsequently, removing the binder filling between theparticles, another method of removing a part of a resist formed on thewafer 702 for LEDs, filling the removed portion with the materialconstituting the uneven structure L (for example, deposition, sputteringmethod, electroforming or the like), and finally, removing the resist,still another method of depositing the material of the uneven structureL on the wafer 702 for LEDs, and directly processing the depositedmaterial of the uneven structure L, and the like.

It is possible to manufacture the uneven structure 720 by preparing theuneven structure L by the above-mentioned method, and next, preparingthe uneven structure A.

As the method of providing the uneven structure A on the unevenstructure L, among the methods are the transfer method, photolithographymethod, thermal lithography method, electron beam lithography method,interference exposure method, lithography method using nanoparticles asa mask, lithography method using a self-organizing structure as a maskand the like. Particularly, from the viewpoints of processing accuracyand processing speed of the uneven structure of the wafer pattern forLEDs, it is preferable to adopt the lithography method usingnanoparticles as a mask or the transfer method. The transfer method willbe described later.

Further, it is possible to manufacture the uneven structure 720 bypreparing the uneven structure A, and next, preparing the unevenstructure L.

As the method of providing the uneven structure A, among the methods arethe transfer method, photolithography method, thermal lithographymethod, electron beam lithography method, interference exposure method,lithography method using nanoparticles as a mask, lithography methodusing a self-organizing structure as a mask and the like. Particularly,from the viewpoints of processing accuracy and processing speed of theuneven structure, it is preferable to adopt the lithography method usingnanoparticles as a mask or the transfer method. The transfer method isas described in the pattern wafer (1) for LEDs.

It is possible to manufacture the uneven structure 720 by preparing theuneven structure L on the wafer for LEDs provided with the unevenstructure A.

It is possible to manufacture the uneven structure 720 by furtherprocessing the uneven structure A. As the method of further processingthe uneven structure A, it is possible to manufacture by the transfermethod, photolithography method, thermal lithography method, electronbeam lithography method, interference exposure method, lithographymethod using nanoparticles as a mask, lithography method using aself-organizing structure as a mask and the like. Particularly, from theviewpoints of processing accuracy and processing speed of the unevenstructure of the pattern wafer (2) 710 for LEDs, it is preferable toadopt the photolithography method or the transfer method. The transfermethod is as described in the pattern wafer (1) for LEDs.

In the case of separately providing the uneven structure layer havingthe uneven structure 720 on the wafer 702 for LEDs, it is possible tomanufacture the uneven structure 720 by preparing the uneven structureA, and next, preparing the uneven structure L.

As the method of providing the uneven structure A, among the methods arethe transfer method, photolithography method, thermal lithographymethod, electron beam lithography method, interference exposure method,lithography method using nanoparticles as a mask, lithography methodusing a self-organizing structure as a mask and the like. Particularly,from the viewpoints of processing accuracy and processing speed of theuneven structure, it is preferable to adopt the lithography method usingnanoparticles as a mask or the transfer method. The transfer method isas described in the pattern wafer (1) for LEDs.

It is possible to manufacture the pattern wafer (2) 710 for LEDs byseparately providing the uneven structure L on the wafer for LEDsprovided with the uneven structure A.

As the method of separately providing the uneven structure L, examplesthereof are the transfer method, and a method of forming a thin filmwith particles included therein on the wafer 702 for LEDs, andsubsequently, removing the binder filling between the particles.Further, there is another method of removing a part of a resist formedon the wafer 702 for LEDs, filling the removed portion with the materialconstituting the uneven structure L (for example, deposition, sputteringmethod, electroforming or the like), and finally, removing the resist.Furthermore, there is still another method of depositing the material ofthe uneven structure L, and directly processing the deposited film ofthe uneven structure L.

EXAMPLES

Examples performed to confirm the effects of the present invention willbe described below.

Symbols used in the following description represent the followingmeaning.

DACHP . . . Fluorine-containing urethane (meth)acrylate (OPTOOL(Registered Trademark) DAC HP (made by Daikin Industries, Ltd.))

M350 . . . Trimethylolpropane (EO-modified) triacrylate (made byTOAGOSEI Co., Ltd. M350)

I.184 . . . 1-Hydroxy-cyclohexyl-phenyl-ketone (made by BASF CompanyIrgacure (Registered Trademark; the same in the following description)184)

I.369 . . . 2-Benzyl-2-dimethylamino-1-(4-morpholino phenyl)-butanone-1(made by BASF Company Irgacure 369)

TTB . . . Titanium (IV) tetrabutoxide monomer (made by Wako PureChemical Industries, Ltd.)

SH710 . . . Phenyl-modified silicone (made by Dow Corning Toray Co.,Ltd.)

3APTMS . . . 3-Acryloxypropyl trimethoxysilane (KBM5103 (made byShin-Etsu silicone corporation))

MEK . . . Methyl ethyl ketone

MIBK . . . Methyl isobutyl ketone

DR833 . . . Tricyclodecane dimethanol diacrylate (SR833 (made bySARTOMER company))

SR368 . . . Tris(2-hydroxyethyl) isocyanurate triacrylate (SR833 (madeby SARTOMER company))

The pattern wafer (1) for LEDs was prepared, the epitaxial wafer forLEDs was prepared using the pattern wafer (1) for LEDs, and the internalquantum efficiency IQE and cracks were evaluated. Next, chipping wasperformed to compare efficiency of LEDs.

In the following study, in order to prepare the pattern wafer (1) forLEDs, first, (1) a cylindrical master mold was prepared, and (2) areel-shaped resin mold was prepared by applying a light transfer methodto the cylindrical master mold. (3) Subsequently, the reel-shaped resinmold was processed to a film for nano-fabrication. Next, (4) using thefilm for nano-fabrication, the pattern wafer (1) for LEDs was prepared.Finally, (5) using the pattern wafer (1) for LEDs, the epitaxial waferfor LEDs was prepared, and performance was evaluated. In addition, theuneven structure A was controlled by an uneven structure of thecylindrical master mold prepared in (1), the light transfer methodperformed in (3), and the film for nano-fabrication prepared in (4).

(1) Preparation of Cylindrical Master Molds

An uneven structure was formed on a surface of cylindrical quartz glassby a direct-write lithography method using a semiconductor laser. First,a resist layer was formed on the cylindrical quartz glass surface by asputtering method. The sputtering method was performed with power of RF100 W using CuO of 3-inches (containing 8 atm % Si) as a target (resistlayer) to form a resist layer of 20 nm. Next, while rotating thecylindrical quartz glass, the entire surface was exposed using asemiconductor laser with a wavelength of 405 nm. Subsequently, pulseexposure was performed on the exposed resist layer using thesemiconductor laser with a wavelength of 405 nm. In addition, the pulsepattern was set to be an regular-hexagonal arrangement. Next, theexposed resist layer was developed. The development of the resist layerwas performed for 240 seconds using 0.03 wt % glycine aqueous solution.Next, using the developed resist layer as a mask, etching was performedon the etching layer (quartz glass) by dry etching. The dry etching wasperformed using SF₆ as an etching gas on the conditions that theprocessing gas pressure was 1 Pa, and that processing power was 300 W.Finally, only the resist layer residual was peeled off from thecylindrical quartz glass provided with the uneven structure on thesurface, using hydrochloric acid of pH1. The peeling time was 6 minutes.

The uneven structure of the obtained cylindrical quartz glass was coatedwith Durasurf (Registered Trademark, the same in the followingdescription) HD-1101Z (made by HARVES Co., Ltd.) that is afluorine-based mold release agent, heated at 60° C. for 1 hour, andthen, allowed to stand at room temperature for 24 hours to fix. Then,cleaning was performed three times using Durasurf HD-ZV (made by HARVESCo., Ltd.) to obtain a cylindrical master mold.

(2). Preparation of Reel-Shaped Resin Molds

Reel-shaped resin molds G1 were prepared successively using the preparedcylindrical master mold as a mold by applying the photo nanoimprintmethod. Next, using the reel-shaped resin mold G1 as a template,reel-shaped resin molds G2 were obtained successively by applying thephoto nanoimprint method.

The material 1 described below was applied to an easy adhesion surfaceof a PET film A-4100 (made by Toyobo Co., Ltd.: width 300 mm, thickness100 μm) by Micro Gravure coating (made by Yasui Seiki Co., Ltd.) so thatthe coating film thickness was 3 μm. Next, the PET film coated with thematerial 1 was pressed against the cylindrical master mold with a niproll, and was irradiated with ultraviolet rays at a temperature of 25°C. and humidity of 60% under atmospheric pressure using a UV exposureapparatus (H bulb) made by Fusion UV Systems Japan Co., Ltd. so that theintegral amount of exposure below the center of the lamp was 1,500mJ/cm², photo-curing was performed successively, and obtained was areel-shaped resin mold G1 (length 200 m, width 300 mm) with the unevenstructure transferred to the surface. Herein, the adjustment was made bythe pressing force of the nip roll so that the film thickness of a curedproduct of the material 1 provided on the PET film was 1,500 nm.

Next, regarding the reel-shaped resin mold G1 as a template, reel-shapedresin molds G2 were prepared successively by applying the photonanoimprint method. The material 1 was applied to an easy adhesionsurface of the PET film A-4100 (made by Toyobo Co., Ltd.: width 300 mm,thickness 100 μm) by Micro Gravure coating (made by Yasui Seiki Co.,Ltd.) so that the coating film thickness was 3 μm. Next, the PET filmcoated with the material 1 was pressed against the uneven structuresurface of the reel-shaped resin mold G1 with the nip roll (0.1 MPa),and was irradiated with ultraviolet rays at a temperature of 25° C. andhumidity of 60% under atmospheric pressure using the UV exposureapparatus (H bulb) made by Fusion UV Systems Japan Co., Ltd. so that theintegral amount of exposure below the center of the lamp was 1,200mJ/cm², photo-curing was performed successively, and obtained was aplurality of reel-shaped resin molds G2 (length 200 m, width 300 mm)with the uneven structure transferred to the surface.

Material 1 . . . DACHP: M350: I.184: I.369=17.5 g: 100 g: 5.5 g: 2.0 g

(3) Preparation of the Film for Nano-Fabrication

The uneven structure surface of the reel-shaped resin mold G2 was coatedwith a diluent of the following material 2. Next, a diluent of thefollowing material 3 was applied onto the uneven structure surface ofthe reel-shaped resin mold G2 with the material 2 included inside theuneven structure, and the film for nano-fabrication was obtained.

Material 2 . . . TTB: 3APTMS: SH710: I.184: I.369=65.2 g: 34.8 g: 5.0 g:1.9 g: 0.7 g

Material 3 . . . Binding polymer: SR833: SR368: I.184: I.369=38 g: 11.5g: 11.5 g: 1.47 g: 0.53 g

Binding polymer . . . Methyl ethyl ketone solution of two-dimensionalcopolymer of benzyl methacrylate 80 mass % and methacrylic acid 20 mass% (solid 50%, weight average molecular weight 29,000)

(2) The material 2 diluted with a mixed solvent of PGME, acetone andisopropanol was directly applied onto the uneven structure surface ofthe reel-shaped resin mold G2 using the same apparatus as in preparationof the reel-shaped resin mold. Herein, the dilution concentration wasset so that the solid amount included in the coating raw material(material 2 diluted with the mixed solvent) per unit area was smallerthan the volume of the uneven structure per unit area by 20% or more.After coating, the resultant was passed inside an air-fan oven of 105°C. for 5 minutes, and the reel-shaped resin mold G2 with the material 2included inside the uneven structure was wound and collected.

Next, while winding off the reel-shaped resin mold G2 with the material2 included inside the uneven structure, the material 3 diluted with amixed solvent of PGME, MEK, MIBK and acetone was directly applied ontothe uneven structure surface using the same apparatus as in (2)preparation of the reel-shaped resin mold. Herein, setting was made sothat the distance between the interface between the material 2 arrangedinside the uneven structure and the applied material 3 and the surfaceof the material 3 was 400 nm to 800 nm. After coating, the resultant waspassed inside the air-fan oven of 105° C. for 5 minutes, a cover filmcomprised of a PET film provided with mold release treatment was bondedto the surface of the material 3, and the resultant was wound andcollected.

(4) Manufacturing of the Pattern Wafer (1) 10 for LEDs

As the pattern wafer (1) 10 for LEDs, used was a sapphire wafer of4-inches of C-surface (0001) with orientation flat existing on theA-surface (11-20).

UV-O₃ treatment was performed on the sapphire wafer for 5 minutes toremove particles on the surface, and the surface was made hydrophilic.Next, the material 3 surface of the film for nano-fabrication was bondedto the sapphire wafer. Herein, the uneven structure of the reel-shapedresin mold G2 was the uneven structure with a plurality of concaveportions in an regular-hexagonal arrangement. In other words, the filmfor nano-fabrication included the reel-shaped resin mold G2 providedwith the concave portion arrangement with 6-fold symmetry. Herein, thecrystal axis of the sapphire wafer and the arrangement axis A of theuneven structure of the film for nano-fabrication were adjusted withinthe predetermined range of the rotation shift angle Θ to bond. Thebonding was performed, while adjusting the rotation shift angle Θ in astate in which the sapphire wafer was heated to 110° C. Next, using ahigh-pressure mercury-vapor lamp light source, using a UV-LED lightsource with a center wavelength of 365 nm, the light was applied overthe reel-shaped resin mold G2 so that the integral light amount was1,200 mJ/cm². Subsequently, the reel-shaped resin mold G2 was peeledoff.

Etching (oxygen ashing) using oxygen gas was performed from the material2 surface side of the obtained layered product (layered productcomprised of material 2/material 3/sapphire wafer), nano-fabrication wasperformed on the material 3 by using the material 2 as the mask, and thesapphire wafer surface was partially exposed. The oxygen ashing wasperformed on the conditions of processing gas pressure of 1 Pa and powerof 300 W. Next, reactive ion etching using a mixed gas of BCl₃ gas andCl₂ gas was performed from the material 2 surface side, and the sapphirewafer was subjected to nano-fabrication. The etching was performed onthe conditions that ICP: 150 W, BIAS: 50 W, and pressure 0.2 Pa, and areactive ion etching apparatus (RIE-101iPH, made by SAMCO Inc.) wasused.

Finally, the resultant was cleaned with a solution obtained by mixingsulfuric acid and hydrogen peroxide solution in a weight ratio of 2:1,and a plurality of sapphire wafers each provided with the unevenstructure 20 i.e. uneven structure A on its surface was obtained.

The shape of the top of the convex-portion of the uneven structure Aprepared on the sapphire wafer was adjusted with processing time of thereactive ion etching. In other words, the shape with a tabletop on thetop of the convex-portion was prepared by halting the reactive ionetching before the material 3 completely disappeared, and the roundedvertex portion without having any tabletop on the top of theconvex-portion was prepared by performing the reactive ion etching untilthe material 3 completely disappeared. Further, by performing thereactive ion etching excessively i.e. applying over etching, thediameter (Φ) of the bottom portion of the convex portion was adjusted.

(5) Preparation of the Epitaxial Wafer for LEDs

On the obtained pattern wafer (1) for LEDs, as a buffer layer, alow-temperature growth buffer layer of Al_(x)Ga_(1-x)N (0≦x≦1) wasdeposited in 1.00 Å. Next, as the undoped first semiconductor layer,undoped GaN was deposited, and as the doped first semiconductor layer,Si-doped GaN was deposited. Next, a distortion absorption layer wasprovided, and then, as the light emitting semiconductor layer, an activelayer of multiple quantum well (well layer, barrier layer=undoped InGaN,Si-doped GaN) with a respective film thickness of 60 Å or 250 Å wasalternately layered so that the number of well layers was 6 and that thenumber of barrier layers was 7. On the light emitting semiconductorlayer, as the second semiconductor layer, Mg-doped AlGaN, undoped GaNand Mg-doped GaN were layered so as to include an electro-blockinglayer. Next, ITO was deposited, and electrode pads were attached afteretching processing. In this state, using a probe, a current of 20 mA waspassed between the p electrode pad and the n electrode pad, and lightemission output was measured.

The internal quantum efficiency IQE was determined from PL intensity.The internal quantum efficiency IQE is defined as (the number of photonsemitted from the light emitting semiconductor layer per unit time/thenumber of electrons injected into the semiconductor light emittingdevice per unit time). In this Embodiment, as an indicator to evaluatethe above-mentioned internal quantum efficiency IQE, (PL intensitymeasured at 300K/PL intensity measured at 10K) was adopted.

The light extraction efficiency LEE was calculated from the lightemission output and the internal quantum efficiency IQE to determine.

Cracks were judged by performing observation on the epitaxial wafer forLEDs with disposition of the semiconductor layer stopped in a facetformation process, from the semiconductor layer surface side, using alight microscope, atomic force microscope and scanning electronmicroscope. Further, in addition thereto, the epitaxial wafer for LEDswas cut, and scanning electron microscope observation was performed onthe cross section of the semiconductor layer to evaluate cracks.

Example 1, Comparative Example 1

In Example 1 and Comparative Example 1 was examined the effect of theshape of the top of the convex-portion. The shape of the top of theconvex-portion was observed using the scanning electron microscope. Theuneven structure A was an regular-hexagonal arrangement. That is, thestructure A was an arrangement with 6-fold symmetry. Further, as theaverage interval Pave, two types of 300 nm and 900 nm were prepared. Therotation shift angle Θ was set at 300. Under the conditions, comparisonwas made between the case (Example 1) where the top of theconvex-portion was in the shape of a rounded corner portion, and thecase (Comparative Example 1) with a tabletop. In addition, the shape incross section of the top of the convex-portion of Example 1 was theshape of a cone.

[Table 1]

As can be seen from Table 1, in the case (Example 1) where the shape ofthe top of the convex-portion was a rounded corner portion, it isunderstood that the internal quantum efficiency IQE was increased, andthat cracks were reduced. First, for the internal quantum efficiencyIQE, in the case (Example 1) where the shape of the top of theconvex-portion was a rounded corner portion, it was confirmed thatdislocations collided and disappeared near the concave portion of theuneven structure A from transmission electron microscope observation,and therefore, the reason is conceivable that the dislocation densitywas decreased. On the other hand, in the case (Comparative Example 1)where the tabletop existed on the top of the convex-portion, it wasobserved that a dislocation occurred from above the tabletop, and grewin the thickness direction of the semiconductor layer. In other words,since the frequency of collision between dislocations was low and thedislocation density was high, it is considered that the degree ofimprovements in internal quantum efficiency IQE was low. Next, forcracks, when growth of the semiconductor layer was stopped during thegrowth to perform detailed observation using scanning electronmicroscope observation on the surface, in the case (Example 1) where thetop of the convex-portion was rounded, it was observed that thesemiconductor layer grew preferentially from the concave portion of theuneven structure A and that growing semiconductor layers coalescedexcellently. More specifically, when focused on opening portions ofhexagons by formed facets, cracks are the density of cracks traveling inthe direction perpendicular to the mutually opposite sides in someopening portion and another opening portion adjacent thereto. In thecase where the average interval Pave was 300 nm or 900 nm, the crackdensity was 39×10⁹/cm² or 41×10⁹/cm², respectively. On the other hand,in the case (Comparative Example 1) where the tabletop existed on thetop of the convex-portion, it was observed that voids were formedpartially near the outer edge portion of the vertex portion of theconvex portion formed of the top of the convex-portion and the sidesurface portion of the convex portion, by the effect of thesemiconductor layer growing from above the top of the convex-portion. Itis presumed that cracks occurred with the voids as a trigger. Morespecifically, in the case where the average interval Pave was 300 nm or900 nm, the crack density was 93×10⁹/cm² or 99×10⁹/cm², respectively.

Example 2, Comparative Example 2

In Example 2 and Comparative Example 2 was examined the effect of therotation shift angle Θ. The arrangement of the uneven structure A was anregular-hexagonal arrangement i.e. arrangement with 0.6-fold symmetry.Further, all the average intervals Pave were set at 300 nm, and all theshapes of the top of the convex-portions were rounded corner portions,and were made the same shape of Example 1. The rotation shift angle Θwas made a parameter, and changed to 0° to 300 every 100. The evaluatedsamples are summarized in Table 2. In the samples as described in Table2, the internal quantum efficiency IQE was approximately the same ineach of the samples, and was about 90%.

[Table 2]

The crack of the evaluation item of Table 2 was normalized with the case(Comparative Example 2) where the rotation shift angle Θ was 0° as 1.More specifically, as the rotation shift angle Θ was changed to 0°, 10°,20°, and 30°, the crack density was 81×10⁹/cm², 72×10⁹/cm², 58×10⁹/cm²,and 53×10⁹/cm², respectively. From Table 2, it is understood that cracksare reduced, as the rotation shift angle Θ is increased. As the reason,by increasing the rotation shift angle Θ, it is conceivable thatadherence properties of the nucleus of the semiconductor layer are madeexcellent to the bottom portion of the concave portion of the unevenstructure A, and that the density of convex portions that growingsemiconductor layer passes is decreased. Further, the reason why cracksare made excellent as the rotation shift angle is increased is presumedby the effect of the diameter of the bottom of the convex-portion. Inother words, in consideration of the density of convex portions passedby the growing semiconductor layer including the diameter of the bottomof the convex-portion, it is conceivable this is because reductions inthe density are remarkable from the point at which the rotation shiftangle Θ exceeds about 20°.

As described above, from Example 1 and Example 2, it was understood thatsuch a region is preferable that the top of the convex-portion of theuneven structure A is a rounded corner portion, and that the rotationshift angle Θ exceeds 0°. As described in FIGS. 13 and 14 already asanother study, since the FWHM of the semiconductor layer and the CL darkspot density were effectively improved in a region where the crackdensity was 70×10⁹/cm² or less, it is conceivable that the crystalquality of the semiconductor layer is significantly enhanced due to theeffect of crack suppression, by setting the rotation shift angle Φ toexceed 0°, and concurrently, making the shape of the top of theconvex-portion a corner portion with a radius of curvature exceeding“0”. In addition, in this Embodiment, controllability of the rotationshift angle Φ is ±1°. When the rotation shift angle Φ was 10° or more,suppression of cracks was more effective. Particularly, it is understoodthat the effect of crack reduction is increased as the rotation shiftangle Θ is increased to 10°, 20°, and 30°. In addition, the mostpreferable case was the case where Θ was 30° i.e. (180/n)°=(180/6)°. Inaddition, although there was a difference in the absolute value, thesame tendency was observed in the pattern wafer (1) for LEDs having theshape of FIG. 15. From the fact, it was understood that it is possibleto exploit the effect of the rotation shift angle Θ and to effectivelysuppress cracks, by using the pattern wafer (1) for LEDs including theuneven structure A comprised of top of the convex-portions each havingthe corner portion with a radius of curvature exceeding “0”.

Example 3

In Example 3 were examined more preferable ranges of the averageinterval Pave. The uneven structure A of the pattern wafer (1) for LEDswas made an regular-hexagonal arrangement (arrangement with 6-foldsymmetry), the shape of the top of the convex-portion was made a roundedcorner portion, the cross-sectional shape of the top of theconvex-portion was made in the shape of a dome, and the rotation shiftangle Θ was set at 300. The parameter was the average interval Pave, andwas adjusted in a range of 200 nm to 1800 nm. The prepared samples aresummarized in Table 3.

[Table 3]

From Table 3, it was understood that the internal quantum efficiency IQEis increased as the average interval Pave is smaller. As the reason, itis presumed that the density of the uneven structure A is increased asthe average interval Pave is decreased, and that it is thereby todisperse dislocations of the semiconductor layer. More specifically, itis conceivable that it is possible to increase the frequency ofcoalescence of growing semiconductor layers, and to disperse coalescenceportions. Particularly, it was confirmed that this phenomenon wasdeveloped when the shape of the top of the convex-portion was therounded corner portion. In other words, dislocations were confirmedinside the semiconductor layer positioned on the top of theconvex-portion in preparing the convex portion with a tabletop that isnot described in Table 3. Therefore, there was the tendency that theinternal quantum efficiency IQE was decreased.

In addition, when the light emission output of the LED was evaluated,the output was larger in the case where the average interval was 300 nmthan in the case where the average interval was 200 nm. Further, thelight emission output was larger in the case where the average intervalwas 900 nm than in the case where the average interval was 1200 nm or1500 nm. Furthermore, the output was larger in the case where theaverage interval was 300 nm than in the case where the average intervalwas 900 nm. Thus, it is understood that performance of the LED chip isnot determined by only the extent of the internal quantum efficiencyIQE. This is due to the effect of the light extraction efficiency LEE.In arranging in descending order of the light emission output, theaverage interval Pave was 300 nm, 900 nm, 700 nm, 450 nm, 1200 nm, 200nm and 1800 nm. In the case where the average interval Pave is 300 nm,the reason is conceivable that light diffraction acts extremelystrongly, the number of diffraction modes is limited, and that, however,the diffraction intensity is high in a predetermined direction. Next,when the average interval Pave is 900 nm or 700 nm, it is conceivablethat the diffraction mode intensity is decreased, and that, however, thenumber of diffraction modes is significantly increased. When the averageinterval exceeds 1000 nm, it is conceivable that light scatteringproperties are too strong, the travelling direction of the light guidedinside the LED chip is once disturbed, the probability of re-waveguideis thereby increased, and that the light emission output is decreased.From the foregoing, it was understood that the internal quantumefficiency IQE is increased as the average interval Pave is decreased.Further, as the epitaxial wafer for LEDs, it was understood that theaverage interval Pave preferably ranges from 200 nm to 1200 nm, and morepreferably ranges from 300 nm to 900 nm.

Example 4

In Example 4 were examined more preferable ranges of the Duty of theuneven structure A. The uneven structure A of the pattern wafer (1) forLEDs was made an regular-hexagonal arrangement (arrangement with 6-foldsymmetry), the shape of the top of the convex-portion was made a roundedcorner portion, the cross-sectional shape of the top of theconvex-portion was made in the shape of a dome, the rotation shift angleΘ was set at 30°, and the average interval Pave was set at 700 nm. Theparameter was the Duty, and was adjusted in a range of 0.29 to 0.93. Theprepared samples are summarized in Table 4.

[Table 4]

From Table 4, it is understood that the internal quantum efficiency IQEis significantly changed when the Duty is between 0.86 and 0.93. In thecase of the Duty of 0.93, the reason is conceivable that the size of thebottom portion of the concave portion is smaller than the size of thestable nucleus of the semiconductor layer. In other words, it ispresumed that adherence of the nucleus and growth properties degraded alittle, the effect of dislocation reduction was thereby decreased, andthat the internal quantum efficiency IQE was decreased. On the otherhand, it is understood that the light extraction efficiency LEE isincreased as the Duty is increased. The reason is conceivable that thevolume of the convex portion is increased from the viewpoint of thephoton, and that the number of modes of light diffraction is therebyincreased. In addition, cracks were approximately the same in all thesamples. From the foregoing, in the case of viewing as the epitaxialwafer for LEDs, it is understood that the Duty of the uneven structure Ais preferably less than 0.93. Further, from the viewpoint of moreincreasing the external quantum efficiency EQE, it was understood thatthe Duty is preferably 0.57 or more, and more preferably 0.71 or more.In addition, the crack density was between 40×10⁹/cm² and 50×10⁹/cm².

Example 5

In Example 5 were examined more preferable ranges of the relationshipbetween the thickness of the first semiconductor layer and the unevenstructure A of the epitaxial wafer for LEDs. As parameters, using thefilm thickness (Hbu) of the undoped first semiconductor layer, the filmthickness (Hbun) of the doped first semiconductor layer, and the averageinterval (Pave) and average height of the uneven structure A, evaluatedwere the internal quantum efficiency IQE, crack and warpage of theepitaxial wafer for LEDs.

The study results are summarized in Table 5. In addition, the meaning ofterms as described in Table 5 is as described below.

No.: Control number of the sample

n: Degree of the arrangement of the uneven structure A (n of arrangementwith n-fold symmetry)

Pave: The average interval (Pave) of the uneven structure A with thedimension of “nm”

Have: The average height (Have) of the uneven structure A with thedimension of “nm”

Θ: The rotation shift angle Θ with the dimension of “°”.

Hbun: The film thickness of the first semiconductor layer with thedimension of “nm”

Hbu: The film thickness of the undoped first semiconductor layer withthe dimension of “nm”

Hbun/Have: The ratio of the film thickness of the first semiconductorlayer to the average height (Have) of the uneven structure A of adimensionless value

Hbu/Have: The ratio of the film thickness of the undoped firstsemiconductor layer to the average height (Aave) of the uneven structureA of a dimensionless value

IQE: Internal Quantum Efficiency with the dimension of “%”.

Crack: Cracks generated in the semiconductor layer with the case equalto Example 1 as ◯ and the case equal to Comparative Example 1 as X

Warpage: Evaluation made by regarding the case of interfering withchipping as “X”, and the case without any problem as “◯”

Total: Total evaluation with the IQE and warpage considered

[Table 5]

In addition, Comparative Example 5 as described in Table 5 is the caseof using the flat sapphire wafer without being provided with the unevenstructure and manufacturing the epitaxial wafer for LEDs as in Example1.

Further, in all the samples as described in Table 5, the shape of theconvex portion was provided with a rounded corner portion. Furthermore,the Duty was set at 0.7.

From Table 5, the following description is understood. When theHbun/Have is in a range of 6.0 to 346.2, as compared with the case(Comparative Example 5) without being provided with the unevenstructure, the internal quantum efficiency IQE is increased to 1.17 timeto 1.7 time, and the warpage of the epitaxial wafer for LEDs is alsosuppressed. The Hbu/Have at this point ranges from 3.3 to 203.8. It isunderstood that improvements in internal quantum efficiency IQE andreductions in the warpage are more remarkable when the Hbun/Have rangesfrom 17.6 to 72.5. The Hbu/Have at this point ranges from 9.6 to 42.5.The reason is conceivable that it is possible to disperse and reducedislocations inside the first semiconductor layer due to the unevenstructure A by the Hbun/Have meeting a range of a predetermined value ormore, and that it is possible to thin the film thickness of the firstsemiconductor layer to reduce the warpage by the Hbun/Aave meeting arange of a predetermined value or less. In No. 12, the Hbun/Have is 6.0,the Hbu/Have is 3.3, and both ratios are thus small values. Therefore,as compared with the case (Comparative Example 5) without being providedwith the uneven structure, the increase rate of the internal quantumefficiency IQE is slightly low. It is conceivable this is because thedislocation reduction effect is slightly weak inside the firstsemiconductor layer and limitations are thereby put on increases inperformance as semiconductors of the light emitting semiconductor layerand second semiconductor layer. Further, in No. 1, the Hbun/Have is346.2, Hbu/Have is 203.8, both ratios thus are large values, and it isunderstood that the warpage of the epitaxial wafer for LEDs affectschipping. From the foregoing, it is understood that it is possible toconcurrently improve improvements in internal quantum efficiency IQE andreductions in the warpage with more excellence when the Hbun/Have is inthe predetermined range.

(Pattern Wafer (2) for LEDs)

As described above, the pattern wafer (1) for LEDs is described inExamples 1 to 5. In the following Examples, described is the patternwafer (2) for LEDs with another uneven structure L further added to thepattern wafer (1) for LEDs.

In the following study, using the film for nano-fabrication used inmanufacturing the pattern wafer (1) for LEDs in the above-mentionedExamples 1 to 5, the uneven structure A was prepared on the surface ofthe wafer for LEDs. Next, the uneven structure L was further provided toobtain the pattern wafer (2) for LEDs provided with the uneven structureA and uneven structure L. Finally, using the obtained pattern wafer (2)for LEDs provided with the uneven structures, the epitaxial wafer forLEDs was prepared, chipping was then performed, and the performance wasevaluated. In addition, the uneven structure L was controlled by themask shape and dry etching condition in the photolithography method. Thepreparation was performed as in Example 1, and the mold releasetreatment was performed as in Example 1.

Using the same film for nano-fabrication as the film in manufacturingthe pattern wafer (1) for LEDs of the above-mentioned Examples 1 to 5,the wafer for LEDs was processed. As the pattern wafer for LEDs, usedwas a C-surface (0001) sapphire wafer with orientation flat existing onthe A-surface (0.11-20). In addition, as the size, the wafer for LEDs of4-inches was used.

The shape of the top of the convex-portion of the uneven structure Aprepared on the sapphire surface was controlled as in the pattern wafer(1) for LEDs of Examples 1 to 5.

By further processing the wafer for LEDs with the uneven structure Ai.e. the pattern wafer (1) for LEDs, the uneven structure L wasprepared. A film of novolac resin for photoresist was formed on theuneven structure A of the pattern wafer (1) for LEDs by a spin coatmethod, and was pre-baked on a hotplate of 120° C. Next, lithography wasperformed to prepare the uneven structure L. Herein, the unevenstructure L was made in the dot shape by negative-developing thephotoresist to use. The uneven structure L was made the hole structureby positive-developing the photoresist to use. In both of the cases, asthe uneven structure L, the convex portions or concave portions werearranged in an regular-hexagonal arrangement, and the average intervalPL was set at 3.2 μm.

The obtained pattern wafer (2) for LEDs was observed with the scanningelectron microscope. The dot-shaped uneven structure L was thedot-shaped body as described below.

The average interval PL was 3.2 μm, and the dots were in theregular-hexagonal arrangement.

The bottom-portion diameter of the dot was 2.4 μm, and thebottom-portion shape was approximately circular.

The bottom of the concave-portion between dots was flat.

A flat surface existed on the dot vertex portion, and the dot was in theshape of a circular truncated cone. The flat surface on the dot vertexportion was approximately circular, and the diameter thereof was 1.6 μm.

The dot vertex portion was an approximately circular tabletop, and theuneven structure A was disposed on only the dot vertex portion.

On the other hand, the hole-shaped uneven structure L was thehole-shaped body as described below.

The average interval PL was 3.2 μm, and the holes were in theregular-hexagonal arrangement.

The opening-portion diameter of the hole was 1.5 μm, and theopening-portion shape was approximately circular.

The depth of the hole was 1.4 μm.

The top of the convex-portion between holes was flat, and the unevenstructure A was disposed on only the flat surface.

The shape of the hole was a cone with the approximately circular bottomportion, and the vertex portion of the cone was a corner portion with aradius of curvature exceeding “0”.

Further, another uneven structure L was also prepared. First, a film ofspin-on glass was formed on the uneven structure A of the pattern wafer(1) for LEDs by the spin coat method, and then, was baked to be SiO₂. Atthis point, it was confirmed that the uneven structure A was flattenedby SiO₂. Next, a film of novolac resin for photoresist was formed on theSiO₂ by the spin coat method, and was baked on the hotplate of 120° C.Next, lithography was performed to process only the SiO₂, and the unevenstructure L was prepared. Herein, the photoresist underwent positivedevelopment, and approximately disk-shaped SiO₂ was partially preparedon the surface of the uneven structure A. The average interval PL wasset at 3.2 μm, and the arrangement was made an regular-hexagonalarrangement.

The obtained pattern wafer (2) for LEDs was observed with the scanningelectron microscope, and the SiO₂ pattern (uneven structure L) was thedot-shaped body as described below.

The average interval PL was 3.2 μm, and the dots were in theregular-hexagonal arrangement.

The bottom-portion diameter of the dot was 1.5 μm, and thebottom-portion shape was approximately circular.

The uneven structure A was provided on the bottom of the concave-portionbetween dots.

On the obtained pattern wafer (2) for LEDs, as a buffer layer, alow-temperature growth buffer layer of Al_(x)Ga_(1-x)N (0≦x≦1) wasdeposited in 100 Å. Next, as the undoped first semiconductor layer,undoped GaN was deposited, and as the doped first semiconductor layer,Si-doped GaN was deposited. Next, a distortion absorption layer wasprovided, and then, as the light emitting semiconductor layer, an activelayer of multiple quantum well (well layer, barrier layer=undoped InGaN,Si-doped GaN) with a respective film thickness of 60 Å or 250 Å wasalternately layered so that the number of well layers was 6 and that thenumber of barrier layers was 7. On the light emitting semiconductorlayer, as the second semiconductor layer, Mg-doped AlGaN, undoped GaNand Mg-doped GaN were layered so as to include an electro-blockinglayer. Next, ITO was deposited, and electrode pads were attached afteretching processing. In this state, using the probe, a current of 20 mAwas passed between the p electrode pad and the n electrode pad, andlight emission output was measured.

The internal quantum efficiency IQE was determined from PL intensity.The internal quantum efficiency IQE is defined as (the number of photonsemitted from the light emitting semiconductor layer per unit time/thenumber of electrons injected into the LED per unit time). In thisEmbodiment, as an indicator to evaluate the above-mentioned internalquantum efficiency IQE, (PL intensity measured at 300K/PL intensitymeasured at 10K) was adopted.

The light extraction efficiency LEE was calculated from the lightemission output and the internal quantum efficiency IQE to determine.

Cracks were judged by performing observation using a light microscope,atomic force microscope and scanning electron microscope, from thesemiconductor layer surface side of the epitaxial wafer for LEDs withthe semiconductor layer deposited; Further, in addition thereto, theepitaxial wafer for LEDs was cut, and scanning electron microscopeobservation was performed on the cross section of the semiconductorlayer to evaluate cracks. In addition, for the evaluation of cracks wasused the wafer with disposition of the semiconductor layer stoppedduring facet formation.

Example 6, Comparative Example 6

The following items were examined in Example 6.

1. Comparison between Patterned Sapphire Substrate (PSS) of conventionaltechniques i.e. pattern wafer for LEDs with only the uneven structure Land the pattern wafer (2) for LEDs having both the uneven structure Aand the uneven structure L

2. Effect of the shape of the top of the convex-portion of the unevenstructure A

3. Difference between the dot-shaped uneven structure L and thehole-shaped uneven structure L

4. Difference between the case where the uneven structure A was providedon the top of the convex-portion of the uneven structure L and the casewhere the uneven structure A was provided on the bottom of theconcave-portion of the uneven structure L

The shape of the top of the convex-portion of the uneven structure A wasobserved using the scanning electron microscope. The uneven structure Awas the regular-hexagonal arrangement. That is, the structure A was anarrangement with 6-fold symmetry. Further, the average interval PA wasset at 300 nm, and the diameter of the bottom of the convex-portion wasset at 220 nm. The rotation shift angle Θ was set at 30°. Under theconditions, each of the case where the top of the convex-portion was inthe shape of a rounded corner portion and the case with a tabletop wasprepared by changing the processing time of reactive ion etching. Inaddition, in assuming the cross-sectional shape of the convex portion,in the counter of the cross section, the shape of the rounded cornerportion is a shape that curves slightly bulged upward in the shape of aconvexity cross each other on the vertex portion of the convex portion.In other words, the side surface portion of the convex portion is theshape slightly bulged upward. Further, in the PSS that was a sample ofComparative Example 6, only the uneven structure L was prepared by thephotolithography method as described above. The prepared samples aredescribed in Table 6.

The meaning of terms as described in Table 6 is as described below.

n . . . Degree of rotational symmetry of the uneven structure A.

PA . . . The average interval of the uneven structure A with thedimension of “nm”.

Θ . . . The rotation shift angle Θ of the uneven structure A with thedimension of “°”

Top of the convex-portion shape . . . Shape of the vertex portion of theconvex portion of the uneven structure A. The tabletop (100 nm) meansthat the diameter of the flat surface of the vertex portion of theconvex portion of the uneven structure A was 100 nm.

m . . . Degree of rotational symmetry of the uneven structure L.

PL . . . The average interval of the uneven structure L with thedimension of “nm”.

Structure . . . In the case of providing the uneven structure L bydirectly processing the uneven structure A by the above-mentionedmethod, the case where the uneven structure L was in the shape of dotsis described as dot, and the case where the uneven structure L was inthe shape of holes is described as holl. Further, the case of providingconvex portions of the uneven structure L made of SiO₂ separately on thesurface of the uneven structure A is described as SiO₂. These terms arealso used in Examples 7 to 9, and are the same meaning.

A on L . . . Case where the uneven structure A was disposed on thevertex-portion top surface of the convex portion of the uneven structureL

A in L . . . Case where the uneven structure A was disposed in thebottom portion of the concave portion of the uneven structure L

PL/PA . . . Ratio between the average interval PL and the averageinterval PA

IQE . . . Internal Quantum Efficiency with a value calculated by themethod described already. The dimension is “%”.

Light emission output ratio . . . Light emission output normalized withthe case (Comparative Example 6) of only the uneven structure L as “1”

Crack . . . Cracks observed with the light microscope. Δ represents thecase where LED chips with abnormality occurring in the light-emissionoutput were 10% or more,

◯ represents the case where such chips were 5% or more and less than10%, and ⊚ represents the case where such chips were less than 5%.

[Table 6]

As can be seen from Table 6, as compared with the case (ComparativeExample 6) with only the uneven structure L, in the case where both theuneven structure A and the uneven structure are provided, it isunderstood that all the crack, internal quantum efficiency IQE and lightemission output are improved. In the case of Comparative Example 6, itis due to the fact that it is possible to increase the light extractionefficiency LEE by the uneven structure L of micro-scale, the density ofthe uneven structure L is low, and that it is thereby not possible toimprove the internal quantum efficiency IQE. By the uneven structure Abeing provided, it was confirmed that dislocations disappeared and werereduced from transmission electron microscope observation. In otherwords, in the case where the uneven structure A is provided, it ispossible, to start growth of the semiconductor layer from the concaveportion of the uneven structure A. By this means, dislocations arereduced. Further, reductions in the dislocation are based on coalescenceof growing semiconductor layers as the principles, and therefore, thecoalescence portions are capable of being dispersed by the unevenstructure A. By this means, residual stress to the semiconductor layerwas reduced, and it is presumed that cracks were suppressed.

In the case where both the uneven structure. A and the uneven structureL are provided, it is understood that the shape of the vertex portion ofthe convex portion of the uneven structure A affects more strongly thanthe uneven structure L species. In the case where the shape of thevertex portion of the convex portion of the uneven structure A is arounded corner portion, it is understood that the internal quantumefficiency IQE is more increased, and that cracks are reduced. First,for the internal quantum efficiency IQE, in the case where the shape ofthe top of the convex-portion was a rounded corner portion, it wasconfirmed that the probability that dislocations collide with each todisappear was high near the concave portion of the uneven structure bytransmission electron microscope observation. The crack densityestimated from the scanning electron microscope observation image was51˜57×10⁹/cm², in the case where the shape of the vertex portion of theuneven structure A was a rounded corner portion. On the other hand, inthe case where the tabletop existed on the vertex portion, it wasobserved that dislocations were generated from above the tabletop, andgrew in the thickness direction of the semiconductor layer. Further,when growth of the semiconductor layer was stopped during the growth,and the surface was observed in detail using scanning electronmicroscope observation, in the case of the rounded top of theconvex-portion, it was observed that the semiconductor layer grewpreferentially from the concave portion of the uneven structure, andthat growing semiconductor layers coalesced excellently. The crackdensity estimated from the scanning electron microscope observationimage was 82˜89×10⁹/cm². On the other hand, in the case where thetabletop existed on the top of the convex-portion, by the effect of thesemiconductor layer growing from above the top of the convex-portion, itwas observed that the frequency of partial formation of voids wasslightly high near the outer edge portion of the vertex portion of theconvex portion formed of the top of the convex-portion and the sidesurface portion of the convex portion. In other words, from theviewpoints of increasing the frequency of collision of dislocations andeffectively reducing the dislocation density, it was understood that thetop of the convex-portion of the uneven structure A is a corner portionwith a radius of curvature exceeding “0”. In addition, these tendencieswere capable of being observed as the similar tendencies in the shape ofthe convex portion as described in FIG. 15.

Further, by comparing arrangements of the uneven structure A withrespect to the uneven structure L, it was understood that the increasein internal quantum efficiency IQE was the highest in the case where theuneven structure A was provided in the bottom of the concave-portion ofthe uneven structure L. In the study, a plurality of convex portions ofthe uneven structure L made of SiO₂ was provided on the surface of theuneven structure A. In other words, the study was made on the conditionthat growth of the semiconductor layer was not started from the top ofthe convex-portion of the uneven structure L. Therefore, it was possibleto grow the semiconductor layer preferentially from the concave portionof the uneven structure L. Herein, since the uneven structure A wasprovided in the bottom of the concave-portion of the uneven structure L,based on the phenomenon as described already, it is considered thatdislocations of the semiconductor layer were reduced, and that crackswere suppressed.

Example 7, Comparative Example 7

In Example 7 was examined the effect of the rotation shift angle Θ. Thearrangement of the uneven structure A was an regular-hexagonalarrangement i.e. arrangement with 6-fold symmetry. Further, all theaverage intervals PA were set at 300 nm, all the shapes of the top ofthe convex-portions were rounded corner-portions, and all the diametersof the bottom of the convex-portions were set at 220 nm. The rotationshift angle Θ was made a parameter, and changed to 0° to 300 every 10°.Further, as the uneven structure L, two types of hole type (holl) andSiO₂ were prepared and evaluated. The case of hole type was made A on L,and the case of SiO₂ was made A in L. The evaluated samples aresummarized in Table 7.

[Table 7]

In the samples as described in Table 7, the internal quantum efficiencyIQE was approximately the same in each of the samples in the case thatthe uneven structure was the hole type, and was about 75%. Further, theinternal quantum efficiency IQE was also approximately the same in eachof the samples in the case that the uneven structure was SiO₂, and wasabout 85%.

The crack of the evaluation item of Table 7 was normalized with the casewhere the rotation shift angle Θ is 0° as 1 to describe. Morespecifically, in the case where the uneven structure L was the holetype, as the rotation shift angle Θ was changed to 0°, 10°, 20°, and30°, the crack density was changed to 99×10⁹/cm², 87×10⁹/cm²,69×10⁹/cm², and 66×10⁹/cm², respectively. On the other hand, in the casewhere the uneven structure was SiO₂, the crack density was changed to81×10⁹/cm², 69×10⁹/cm², 56×10⁹/cm², and 54×10⁹/cm². From Table 7, it isunderstood that cracks are reduced, as the rotation shift angle Θ isincreased. This is because the effect of the uneven structure A of thepattern wafer (1) for LEDs is exerted also in the case of providing theuneven structure L. In addition, these tendencies were capable of beingobserved as the similar tendencies in the shape of the convex portion asdescribed in FIG. 15.

As described above, from Example 6 and Example 7, it was understood thatit is possible to improve the internal quantum efficiency IQE, lightextraction efficiency LEE, and cracks by providing both the unevenstructure A and the uneven structure L. Further, it was understood thatthe increase of the internal quantum efficiency IQE and cracksuppression effect are more increased when the top of the convex-portionof the uneven structure is a rounded corner portion. Furthermore, it wasunderstood that the semiconductor layer with cracks suppressed and highinternal quantum efficiency IQE was deposited when the rotation shiftangle Φ was 10° or more. Particularly, it is understood that the effectof warpage reduction is increased as the rotation shift angle Θ isincreased to 10°, 20°, and 30°. In addition, the most preferable casewas the case where Θ was 30° i.e. (180/n)°=(180/6)°.

Example 8

In Example 8 were examined more preferable ranges of the ratio of theaverage interval PA and the average interval PL. The uneven structure Aof the pattern wafer (2) for LEDs was made an regular-hexagonalarrangement (arrangement with 6-fold symmetry), the shape of the top ofthe convex-portion was made a rounded corner portion, and the rotationshift angle Θ was set at 30°. The parameter was average intervalPL/average interval PA, and was adjusted by fixing the average intervalPL and changing the average interval PA. The average interval PA wasadjusted in a range of 200 nm to 1800 nm. Further, as the unevenstructure L, adopted were the hole type (holl) and A on L with theaverage interval PL of 3000 nm. The prepared samples are summarized inTable 8.

[Table 8]

From Table 8, it was understood that the internal quantum efficiency IQEis increased as the ratio (PL/PA) is larger. The reason is conceivablethat the effect of the uneven structure A is capable of being developedmore excellence, as the ratio (PL/PA) is larger, also in the case wherethe uneven structure L is provided. Particularly, the large ratio(PL/PA) means that the presence of the uneven structure A decreases fromthe viewpoint of the uneven structure L. In other words, from theviewpoint of the semiconductor layer flying by CVD, the uneven structureL is first identified. Then, when the layer gets near to the surface ofthe uneven structure L, the layer is capable of first recognizing thepresence of the uneven structure A. In viewing from the other side, itis meant that excellent growth is achieved on the surface of the unevenstructure A without undergoing the effect of large structure of theuneven structure L. Actually, as a result of checking a growth extentwith the scanning electron microscope by halting growth of thesemiconductor layer during the growth, it was confirmed that thefrequency of coalescence of growing semiconductor layers was higher asthe ratio (PL/PA) was larger, and that coalescence portions were-capableof being dispersed. Particularly, it was confirmed that this phenomenonwas developed more excellently when the shape of the top of theconvex-portion was a rounded corner portion. In other words, inpreparing convex portions with respective tabletops arbitrarily,increased was the frequency of identifying dislocations inside thesemiconductor layer positioned on the vertex portion of the convexportion. Therefore, the internal quantum efficiency IQE tended todecrease. From the foregoing, it was understood that the ratio (PL/PA)preferably exceeds 2.7, is more preferably 3.6 or more, and mostpreferably 4.6 or more.

In addition, when the light emission output of LEDs was evaluated, theoutput was higher in the case of the ratio (PL/PA) of 10.7 than in thecase of the ratio (PL/PA) of 16.0. Further, the output was higher in thecase of the ratio (PL/PA) of 3.6 than in the case of the ratios (PL/PA)of 2.7 and 1.8. Furthermore, the output was higher in the case of theratio (PL/PA) of 10.7 than in the case of the ratio (PL/PA) of 3.6.Thus, it is understood that performance of the LED is not determined byonly the degree of the internal quantum efficiency IQE. This is theeffect of the light extraction efficiency LEE. In arranging indescending order of the light emission output, the ratio (PL/PA) was10.7, 3.6, 4.6, 7.1, 2.7, 16.0 and 1.8. In the case where the ratio(PL/PA) is 10.7, the reason is conceivable that light diffraction actsextremely strongly, the number of diffraction modes is limited, andthat, however, the diffraction intensity is high in a predetermineddirection. Next, when the ratio (PL/PA) is 3.6 or 4.6, it is conceivablethat the diffraction mode intensity is decreased, and that, however, thenumber of diffraction modes is significantly increased. When the ratio(PL/PA) falls below 3.6, it is conceivable that light scatteringproperties are too strong, the travelling direction of the light guidedinside the LED is once disturbed, the probability of re-waveguide isthereby increased, and that the light emission output is decreased. Fromthe foregoing, it was understood that the internal quantum efficiencyIQE is increased as the ratio (PL/PA) is increased. Further, as the LED,it was understood that the ratio (PL/PA) preferably ranges from 2.7 to16.0, and more preferably ranges from 3.6 to 10.7. In addition, the samestudy was made also in the case where the uneven structure L was SiO₂,and the same tendency as in Example 8 was observed.

Example 9

In Example 9 were examined more preferable ranges of the Duty of theuneven structure A. The uneven structure A of the pattern wafer (2) forLEDs was made an regular-hexagonal arrangement (arrangement with 6-foldsymmetry), the shape of the top of the convex-portion was made a roundedcorner portion, the rotation shift angle Θ was set at 300, and theaverage interval PA was set at 300 nm. The parameter was the Duty, andwas adjusted in a range of 0.17 to 0.96. As the uneven structure L wasprepared the hole type (holl) The prepared samples are summarized inTable 9.

[Table 9]

From Table 9, it is understood that the internal quantum efficiency IQEis significantly changed when the Duty is between 0.73 and 0.99. In thecase of the Duty of 0.96, the reason is conceivable that the size of thebottom portion of the concave portion of the uneven structure A issmaller than the size of the stable nucleus of the semiconductor layer.In other words, it is presumed that adherence of the nucleus and growthproperties degraded a little, the effect of dislocation reduction wasthereby decreased, and that the internal quantum efficiency IQE wasdecreased. On the other hand, it is understood that the light extractionefficiency LEE is increased as the Duty is increased. In other words, itis understood that it is possible to add the function of improving thelight extraction efficiency LEE by adjustments of the Duty, in additionto crack suppression and improvements in internal quantum efficiency IQEwhich are the basic functions of the uneven structure A. The reason isconceivable that the volume of the convex portion is increased from theviewpoint of the photon, and that the number of modes of lightdiffraction is increased. In addition, cracks were approximately thesame in all the samples, and were in a range of 49×10⁹/cm² to52×10⁹/cm². From the foregoing, in the case of viewing as the LED, it isunderstood that the Duty of the uneven structure A is preferably lessthan 0.96. Further, from the viewpoint of more increasing the externalquantum efficiency EQE, it was understood that the Duty is preferably0.53 or more, and more preferably 0.63 or more. In addition, the samestudy was made also in the case where the uneven structure L was SiO₂,and the same tendency as in Example 9 was observed.

The present invention is applicable to LEDs, and particularly, issuitably applicable to GaN-based semiconductor light emitting devicesapplied to blue LEDs, ultraviolet LEDs and white LEDs.

The present application is based on Japanese Patent Application No.2013-116025 filed on May 31, 2013, and Patent Application No.2013-116024 filed on May 31, 2013, entire contents of which areexpressly incorporated by reference herein.

TABLE 1 TOP SHAPE OF THE CONVEX- n Pave (nm) θ (°) PORTION IQE (%) CRACKEXAMPLE 1 6 300 30 ROUNDED CORNER PORTION 92 ◯ 6 900 30 ROUNDED CORNERPORTION 86 ◯ COMPARATIVE 6 300 30 TABLETOP (100 nm) 73 Δ EXAMPLE 1 6 90030 TABLETOP (300 nm) 67 Δ

TABLE 2 Pave Θ TOP SHAPE OF THE n (nm) (°) CONVEX-PORTION CRACKCOMPARATIVE 6 300 0 ROUNDED CORNER 1 EXAMPLE 2 PORTION EXAMPLE 2 6 30010 ROUNDED CORNER 0.89 PORTION 6 300 20 ROUNDED CORNER 0.72 PORTION 6300 30 ROUNDED CORNER 0.66 PORTION

TABLE 3 Pave Θ TOP SHAPE OF THE IQE n (nm) (°) CONVEX-PORTION (%)EXAMPLE 3 6 200 30 ROUNDED CORNER 96 PORTION 6 300 30 ROUNDED CORNER 93PORTION 6 450 30 ROUNDED CORNER 91 PORTION 6 700 30 ROUNDED CORNER 88PORTION 6 900 30 ROUNDED CORNER 83 PORTION 6 1200 30 ROUNDED CORNER 76PORTION 6 1800 30 ROUNDED CORNER 68 PORTION

TABLE 4 TOP SHAPE OF THE CONVEX- n Pave (nm) DUTY θ (°) PORTION IQE (%)LEE (%) CRACK EXAMPLE 4 6 700 0.29 30 ROUNDED CORNER PORTION 88 52 ◯ 6700 0.43 30 ROUNDED CORNER PORTION 87 55 ◯ 6 700 0.57 30 ROUNDED CORNERPORTION 89 58 ◯ 6 700 0.71 30 ROUNDED CORNER PORTION 88 63 ◯ 6 700 0.7930 ROUNDED CORNER PORTION 88 65 ◯ 6 700 0.86 30 ROUNDED CORNER PORTION86 67 ◯ 6 700 0.93 30 ROUNDED CORNER PORTION 78 66 ◯

TABLE 5 No. n Pave Have θ Hbun Hbu Hbun/Have Hbu/Have IQE CRACK WARPAGETOTAL EXAMPLE 5 1 6 300 130 30 45000 26500 346.2 203.8 80 ◯ X Δ 2 6 20080 30 5800 3400 72.5 42.5 86 ◯ ◯ ◯ 3 6 200 80 30 3400 2400 42.5 30.0 73◯ ◯ ◯ 4 6 200 150 30 5800 3400 38.7 22.7 89 ◯ ◯ ◯ 5 6 300 150 30 58003400 38.7 22.7 85 ◯ ◯ ◯ 6 6 200 150 30 4400 2400 29.3 16.0 88 ◯ ◯ ◯ 7 6300 150 30 4400 2400 29.3 16.0 84 ◯ ◯ ◯ 8 6 200 150 30 3400 2400 22.716.0 74 ◯ ◯ ◯ 9 6 460 250 30 5800 3400 23.2 13.6 79 ◯ ◯ ◯ 10 6 700 30030 5800 3400 19.3 11.3 74 ◯ ◯ ◯ 11 6 460 250 30 4400 2400 17.6 9.6 76 ◯◯ ◯ 12 6 300 150 30 900 500 6.0 3.3 61 ◯ ◯ Δ COMPARATIVE 0 6 0 0 30 44002400 — — 52 ◯ ◯ X EXAMPLE 5

TABLE 6 UNEVEN STRUCTURE A RESULT TOP UNEVEN UNEVEN LIGHT SHAPESTRUCTURE L STRUCTURE EMISSION PA OF THE PL A, L IQE OUTPUT n (nm) θ (°)CONVEX- m (nm) STRUCTURE AonL AinL PL/PA (%) RATIO CRACK TOTAL EXAMPLE 66 300 30 ROUNDED 6 3200 dot ◯ — 10.7 79 1.21 ⊚ ⊚ CORNER X ◯ — 76 1.19 ⊚⊚ PORTION TABLETOP SiO₂ — ◯ 85 1.29 ⊚ ⊚ dot ◯ — 71 1.14 ◯ ◯ holl ◯ — 691.13 ◯ Δ SiO₂ — ◯ 75 1.19 ◯ ◯ COMPARATIVE — — — — 6 3200 dot — — — 61 1Δ X EXAMPLE 6

TABLE 7 UNEVEN STRUCTURE A UNEVEN TOP SHAPE OF THE STRUCTURE L n PA (nm)θ (°) CONVEX-PORTION STRUCTURE CRACK COMPARATIVE 6 300 0 ROUNDED CORNERHOLL OR SiO₂ 1 EXAMPLE 7 10 PORTION 0.89 EXAMPLE 7 20 0.72 30 0.66

TABLE 8 UNEVEN STRUCTURE A UNEVEN TOP SHAPE OF STRUCTURE L n PA (nm) θ(°) THE CONVEX- STRUCTURE PL/PA IQE/% EXAMPLE 8 6 200 30 ROUNDED CORNERHOLL 16.0 81 300 PORTION 10.7 79 450 7.1 73 700 4.6 68 900 3.6 64 12002.7 53 1800 1.8 45

TABLE 9 UNEVEN STRUCTURE A UNEVEN TOP SHAPE OF STRUCTURE L IQE LEE n PA(nm) DUTY θ (°) THE CONVEX- STRUCTURE (%) (%) CRACK EXAMPLE 9 6 300 0.1730 ROUNDED CORNER HOLL 79 52 ◯ 0.27 PORTION 81 55 ◯ 0.43 78 58 ◯ 0.53 7963 ◯ 0.63 80 65 ◯ 0.73 78 67 ◯ 0.96 64 66 ◯

The invention claimed is:
 1. A pattern wafer for an LED, comprising: anuneven structure A having an arrangement with n-fold rotational symmetryon at least a part of a main surface, wherein in at least a part of theuneven structure A, a minimum rotational shift angle Θ satisfies0°<Θ≦(180/n)°, wherein Θ is the minimum rotational shift angle of anarrangement axis A of the uneven structure A relative to a crystal axisdirection of the pattern wafer for an LED in the main surface, and eachtop of convex-portions of the uneven structure A is formed as a curvedsurface having a radius of curvature exceeding “0”.
 2. The pattern waferfor an LED according to claim 1, wherein the pattern wafer is furtherprovided with an uneven structure L, different from the uneven structureA, having an arrangement with m-fold rotational symmetry, wherein m is ainteger of 2 or more.
 3. The pattern wafer for an LED according to claim2, wherein the uneven structure L is comprised of pluralities of convexportions and concave portions having a first average interval (PL), theuneven structure A is provided on surfaces of at least either the convexportions or the concave portions forming the uneven structure L, and iscomprised of pluralities of convex portions and concave portions havinga second average interval (PA), and a ratio (PL/PA) of the first averageinterval (PL) to the second average interval (PA) exceeds 1 and is 2000or less.
 4. The pattern wafer for an LED according to claim 3, wherein aplurality of the convex portions forming the uneven structure L ismutually spaced, and a plurality of the convex portions or the concaveportions forming the uneven structure A is provided at least in bottomportions of a plurality of the concave portions forming the unevenstructure L.
 5. The pattern wafer for an LED according to claim 3,wherein a plurality of the concave portions forming the uneven structureL is mutually spaced, and a plurality of the convex portions or theconcave portions forming the uneven structure A is provided at least ontops of a plurality of the convex portions forming the uneven structureL.
 6. The pattern wafer for an LED according to claim 3, wherein acoverage of the uneven structure A to the uneven structure L exceeds 0%and is less than 100%.
 7. The pattern wafer for an LED according toclaim 2, wherein the uneven structure A is comprised of pluralities ofconvex portions and concave portions having a first average interval(PA), the uneven structure L is provided on a surface of the unevenstructure A apart from each other so that a part of the uneven structureA is exposed, and is comprised of a plurality of convex portions havinga second average interval (PL), and a ratio (PL/PA) between the firstaverage interval (PA) and the second average interval (PL) exceeds 1 andis 2000 or less.
 8. The pattern wafer for an LED according to claim 1,wherein an average interval Pave of the uneven structure A meets 50nm≦Pave≦1500 nm.
 9. The pattern wafer for an LED according to claim 1,wherein in using a Duty (ΦDave/Pave) that is a ratio of an averagediameter (Φave) of a bottom of the convex-portion of the unevenstructure A to an average interval Pave, the minimum rotational shiftangle Θ meets a range of a tan(Duty/2)°≦Θ≦(180/n)°.
 10. The patternwafer for an LED according to claim 1, wherein the pattern wafer for anLED is a sapphire wafer, a silicon wafer, a silicon carbide wafer or agallium nitride-based wafer.
 11. An epitaxial wafer for an LED, whereinat least a first semiconductor layer, a light emitting semiconductorlayer and a second semiconductor layer are layered in this order on themain surface provided with the uneven structure A of the pattern waferfor an LED according to claim
 1. 12. The epitaxial wafer for an LEDaccording to claim 11, wherein a ratio (Hbun/Have) of a distance (Hbun)between a surface on the light emitting semiconductor layer side of thepattern wafer for an LED and a surface on the first semiconductor layerside of the light emitting semiconductor layer to an average height(Have) of the uneven structure A meets 2≦Hbun/Have≦300.
 13. Theepitaxial wafer for an LED according to claim 11, wherein the firstsemiconductor layer contains an undoped first semiconductor layer and adoped first semiconductor layer sequentially layered from the patternwafer for an LED side, and a ratio (Hbu/Have) of a distance (Hbu)between a surface on the light emitting semiconductor layer side of thepattern wafer for an LED and a surface on the doped first semiconductorlayer side of the undoped first semiconductor layer to an average height(Have) of the uneven structure A meets 1.5≦Hbu/Have≦200.